diff --git a/src/Control/Controller.php b/src/Control/Controller.php
index 299ce72a7..3cc112f61 100644
--- a/src/Control/Controller.php
+++ b/src/Control/Controller.php
@@ -4,6 +4,7 @@ namespace SilverStripe\Control;
 
 use SilverStripe\Core\ClassInfo;
 use SilverStripe\Dev\Debug;
+use SilverStripe\Dev\Deprecation;
 use SilverStripe\ORM\FieldType\DBHTMLText;
 use SilverStripe\Security\Member;
 use SilverStripe\Security\Security;
@@ -455,7 +456,8 @@ class Controller extends RequestHandler implements TemplateGlobalProvider
         $class = static::class;
         while ($class != 'SilverStripe\\Control\\RequestHandler') {
             $templateName = strtok($class ?? '', '_') . '_' . $action;
-            if (SSViewer::hasTemplate($templateName)) {
+            $templateExists = Deprecation::withSuppressedNotice(fn() => SSViewer::hasTemplate($templateName));
+            if ($templateExists) {
                 return $class;
             }
 
@@ -487,7 +489,7 @@ class Controller extends RequestHandler implements TemplateGlobalProvider
             $parentClass = get_parent_class($parentClass ?? '');
         }
 
-        return SSViewer::hasTemplate($templates);
+        return Deprecation::withSuppressedNotice(fn() => SSViewer::hasTemplate($templates));
     }
 
     /**
diff --git a/src/Control/Email/Email.php b/src/Control/Email/Email.php
index 52b05dc94..fd1bc8195 100644
--- a/src/Control/Email/Email.php
+++ b/src/Control/Email/Email.php
@@ -12,6 +12,7 @@ use SilverStripe\Core\Environment;
 use SilverStripe\Core\Extensible;
 use SilverStripe\Core\Injector\Injectable;
 use SilverStripe\Core\Injector\Injector;
+use SilverStripe\Dev\Deprecation;
 use SilverStripe\ORM\FieldType\DBField;
 use SilverStripe\View\ArrayData;
 use SilverStripe\View\Requirements;
@@ -402,9 +403,11 @@ class Email extends SymfonyEmail
             return $this->HTMLTemplate;
         }
 
-        return ThemeResourceLoader::inst()->findTemplate(
-            SSViewer::get_templates_by_class(static::class, '', Email::class),
-            SSViewer::get_themes()
+        return Deprecation::withSuppressedNotice(
+            fn() => ThemeResourceLoader::inst()->findTemplate(
+                SSViewer::get_templates_by_class(static::class, '', Email::class),
+                SSViewer::get_themes()
+            )
         );
     }
 
diff --git a/src/Forms/GridField/GridFieldAddExistingAutocompleter.php b/src/Forms/GridField/GridFieldAddExistingAutocompleter.php
index 8db2bc627..8c2c6f18f 100644
--- a/src/Forms/GridField/GridFieldAddExistingAutocompleter.php
+++ b/src/Forms/GridField/GridFieldAddExistingAutocompleter.php
@@ -17,6 +17,7 @@ use SilverStripe\View\ArrayData;
 use SilverStripe\View\SSViewer;
 use LogicException;
 use SilverStripe\Control\HTTPResponse_Exception;
+use SilverStripe\Dev\Deprecation;
 
 /**
  * This class is is responsible for adding objects to another object's has_many
@@ -283,7 +284,7 @@ class GridFieldAddExistingAutocompleter extends AbstractGridFieldComponent imple
         $json = [];
         Config::nest();
         SSViewer::config()->set('source_file_comments', false);
-        $viewer = SSViewer::fromString($this->resultsFormat);
+        $viewer = Deprecation::withSuppressedNotice(fn() => SSViewer::fromString($this->resultsFormat));
         foreach ($results as $result) {
             if (!$result->canView()) {
                 continue;
diff --git a/src/Forms/GridField/GridFieldDataColumns.php b/src/Forms/GridField/GridFieldDataColumns.php
index 41b0713d9..89aa85177 100644
--- a/src/Forms/GridField/GridFieldDataColumns.php
+++ b/src/Forms/GridField/GridFieldDataColumns.php
@@ -5,6 +5,7 @@ namespace SilverStripe\Forms\GridField;
 use SilverStripe\Core\Convert;
 use InvalidArgumentException;
 use LogicException;
+use SilverStripe\Dev\Deprecation;
 use SilverStripe\View\ViewableData;
 
 /**
@@ -228,16 +229,18 @@ class GridFieldDataColumns extends AbstractGridFieldComponent implements GridFie
      * @param ViewableData $record
      * @param string $columnName
      * @return string|null - returns null if it could not found a value
+     * @deprecated 5.4.0 Will be removed without equivalent functionality to replace it.
      */
     protected function getValueFromRelation($record, $columnName)
     {
+        Deprecation::notice('5.4.0', 'Will be removed without equivalent functionality to replace it.');
         $fieldNameParts = explode('.', $columnName ?? '');
         $tmpItem = clone($record);
         for ($idx = 0; $idx < sizeof($fieldNameParts ?? []); $idx++) {
             $methodName = $fieldNameParts[$idx];
             // Last mmethod call from $columnName return what that method is returning
             if ($idx == sizeof($fieldNameParts ?? []) - 1) {
-                return $tmpItem->XML_val($methodName);
+                return Deprecation::withSuppressedNotice(fn() => $tmpItem->XML_val($methodName));
             }
             // else get the object from this $methodName
             $tmpItem = $tmpItem->$methodName();
diff --git a/src/Forms/HTMLEditor/HTMLEditorField.php b/src/Forms/HTMLEditor/HTMLEditorField.php
index 90c3fad75..285d0ae9e 100644
--- a/src/Forms/HTMLEditor/HTMLEditorField.php
+++ b/src/Forms/HTMLEditor/HTMLEditorField.php
@@ -8,6 +8,7 @@ use SilverStripe\Forms\TextareaField;
 use SilverStripe\ORM\DataObject;
 use SilverStripe\ORM\DataObjectInterface;
 use Exception;
+use SilverStripe\Dev\Deprecation;
 use SilverStripe\View\Parsers\HTMLValue;
 
 /**
@@ -129,7 +130,9 @@ class HTMLEditorField extends TextareaField
      */
     public function saveInto(DataObjectInterface $record)
     {
-        if ($record->hasField($this->name) && $record->escapeTypeForField($this->name) != 'xml') {
+        if ($record->hasField($this->name)
+            && Deprecation::withSuppressedNotice(fn () => $record->escapeTypeForField($this->name)) != 'xml'
+        ) {
             throw new Exception(
                 'HTMLEditorField->saveInto(): This field should save into a HTMLText or HTMLVarchar field.'
             );
diff --git a/src/View/SSTemplateParser.peg b/src/View/SSTemplateParser.peg
index 0f15460f9..76c40ed98 100644
--- a/src/View/SSTemplateParser.peg
+++ b/src/View/SSTemplateParser.peg
@@ -948,7 +948,7 @@ class SSTemplateParser extends Parser implements TemplateParser
         $arguments = $res['arguments'];
 
         // Note: 'type' here is important to disable subTemplates in SSViewer::getSubtemplateFor()
-        $res['php'] = '$val .= \\SilverStripe\\View\\SSViewer::execute_template([["type" => "Includes", '.$template.'], '.$template.'], $scope->getItem(), [' .
+        $res['php'] = '$val .= \\SilverStripe\\View\\SSViewer::execute_template([["type" => "Includes", '.$template.'], '.$template.'], $scope->getCurrentItem(), [' .
             implode(',', $arguments)."], \$scope, true);\n";
 
         if ($this->includeDebuggingComments) { // Add include filename comments on dev sites
diff --git a/src/View/SSTemplateParser.php b/src/View/SSTemplateParser.php
index 9ca62eaa5..c7c273414 100644
--- a/src/View/SSTemplateParser.php
+++ b/src/View/SSTemplateParser.php
@@ -3897,7 +3897,7 @@ class SSTemplateParser extends Parser implements TemplateParser
         $arguments = $res['arguments'];
 
         // Note: 'type' here is important to disable subTemplates in SSViewer::getSubtemplateFor()
-        $res['php'] = '$val .= \\SilverStripe\\View\\SSViewer::execute_template([["type" => "Includes", '.$template.'], '.$template.'], $scope->getItem(), [' .
+        $res['php'] = '$val .= \\SilverStripe\\View\\SSViewer::execute_template([["type" => "Includes", '.$template.'], '.$template.'], $scope->getCurrentItem(), [' .
             implode(',', $arguments)."], \$scope, true);\n";
 
         if ($this->includeDebuggingComments) { // Add include filename comments on dev sites
diff --git a/src/View/SSViewer.php b/src/View/SSViewer.php
index 3b82eb3fd..55f2fc087 100644
--- a/src/View/SSViewer.php
+++ b/src/View/SSViewer.php
@@ -15,6 +15,7 @@ use SilverStripe\ORM\FieldType\DBField;
 use SilverStripe\ORM\FieldType\DBHTMLText;
 use SilverStripe\Security\Permission;
 use InvalidArgumentException;
+use SilverStripe\Dev\Deprecation;
 
 /**
  * Parses a template file with an *.ss file extension.
@@ -86,6 +87,7 @@ class SSViewer implements Flushable
      *
      * @config
      * @var string
+     * @deprecated 5.4.0 Will be moved to SilverStripe\View\SSTemplateEngine.global_key
      */
     private static $global_key = '$CurrentReadingMode, $CurrentUser.ID';
 
@@ -134,6 +136,7 @@ class SSViewer implements Flushable
      * List of items being processed
      *
      * @var array
+     * @deprecated 5.4.0 Will be moved to SilverStripe\View\SSTemplateEngine
      */
     protected static $topLevel = [];
 
@@ -141,6 +144,7 @@ class SSViewer implements Flushable
      * List of templates to select from
      *
      * @var array
+     * @deprecated 5.4.0 Will be moved to SilverStripe\View\SSTemplateEngine
      */
     protected $templates = null;
 
@@ -148,6 +152,7 @@ class SSViewer implements Flushable
      * Absolute path to chosen template file
      *
      * @var string
+     * @deprecated 5.4.0 Will be moved to SilverStripe\View\SSTemplateEngine
      */
     protected $chosen = null;
 
@@ -155,6 +160,7 @@ class SSViewer implements Flushable
      * Templates to use when looking up 'Layout' or 'Content'
      *
      * @var array
+     * @deprecated 5.4.0 Will be moved to SilverStripe\View\SSTemplateEngine
      */
     protected $subTemplates = [];
 
@@ -165,11 +171,13 @@ class SSViewer implements Flushable
 
     /**
      * @var TemplateParser
+     * @deprecated 5.4.0 Will be moved to SilverStripe\View\SSTemplateEngine
      */
     protected $parser;
 
     /**
      * @var CacheInterface
+     * @deprecated 5.4.0 Will be moved to SilverStripe\View\SSTemplateEngine
      */
     protected $partialCacheStore = null;
 
@@ -185,10 +193,11 @@ class SSViewer implements Flushable
     public function __construct($templates, TemplateParser $parser = null)
     {
         if ($parser) {
-            $this->setParser($parser);
+            Deprecation::notice('5.4.0', 'The $parser parameter is deprecated and will be removed');
+            Deprecation::withSuppressedNotice(fn() => $this->setParser($parser));
         }
 
-        $this->setTemplate($templates);
+        Deprecation::withSuppressedNotice(fn() => $this->setTemplate($templates));
 
         if (!$this->chosen) {
             $message = 'None of the following templates could be found: ';
@@ -207,11 +216,15 @@ class SSViewer implements Flushable
 
     /**
      * Triggered early in the request when someone requests a flush.
+     * @deprecated 5.4.0 Will be replaced with SilverStripe\View\SSTemplateEngine::flush()
      */
     public static function flush()
     {
-        SSViewer::flush_template_cache(true);
-        SSViewer::flush_cacheblock_cache(true);
+        Deprecation::withSuppressedNotice(function () {
+            Deprecation::notice('5.4.0', 'Will be replaced with SilverStripe\View\SSTemplateEngine::flush()');
+            SSViewer::flush_template_cache(true);
+            SSViewer::flush_cacheblock_cache(true);
+        });
     }
 
     /**
@@ -220,10 +233,12 @@ class SSViewer implements Flushable
      * @param string $content The template content
      * @param bool|void $cacheTemplate Whether or not to cache the template from string
      * @return SSViewer
+     * @deprecated 5.4.0 Will be replaced with SilverStripe\View\SSTemplateEngine::renderString()
      */
     public static function fromString($content, $cacheTemplate = null)
     {
-        $viewer = SSViewer_FromString::create($content);
+        Deprecation::notice('5.4.0', 'Will be replaced with SilverStripe\View\SSTemplateEngine::renderString()');
+        $viewer = Deprecation::withSuppressedNotice(fn() => SSViewer_FromString::create($content));
         if ($cacheTemplate !== null) {
             $viewer->setCacheTemplate($cacheTemplate);
         }
@@ -325,9 +340,11 @@ class SSViewer implements Flushable
      * Get the current item being processed
      *
      * @return ViewableData
+     * @deprecated 5.4.0 Will be removed without equivalent functionality to replace it.
      */
     public static function topLevel()
     {
+        Deprecation::notice('5.4.0', 'Will be removed without equivalent functionality to replace it.');
         if (SSViewer::$topLevel) {
             return SSViewer::$topLevel[sizeof(SSViewer::$topLevel)-1];
         }
@@ -385,9 +402,11 @@ class SSViewer implements Flushable
 
     /**
      * @param string|array $templates
+     * @deprecated 5.4.0 Will be replaced with SilverStripe\View\SSTemplateEngine::setTemplate()
      */
     public function setTemplate($templates)
     {
+        Deprecation::notice('5.4.0', 'Will be replaced with SilverStripe\View\SSTemplateEngine::setTemplate()');
         $this->templates = $templates;
         $this->chosen = $this->chooseTemplate($templates);
         $this->subTemplates = [];
@@ -398,19 +417,25 @@ class SSViewer implements Flushable
      *
      * @param array|string $templates
      * @return string
+     * @deprecated 5.4.0 Will be removed without equivalent functionality to replace it
      */
     public static function chooseTemplate($templates)
     {
-        return ThemeResourceLoader::inst()->findTemplate($templates, SSViewer::get_themes());
+        Deprecation::notice('5.4.0', 'Will be removed without equivalent functionality to replace it');
+        return Deprecation::withSuppressedNotice(
+            fn() => ThemeResourceLoader::inst()->findTemplate($templates, SSViewer::get_themes())
+        );
     }
 
     /**
      * Set the template parser that will be used in template generation
      *
      * @param TemplateParser $parser
+     * @deprecated 5.4.0 Will be replaced with SilverStripe\View\SSTemplateEngine::setParser()
      */
     public function setParser(TemplateParser $parser)
     {
+        Deprecation::notice('5.4.0', 'Will be replaced with SilverStripe\View\SSTemplateEngine::setParser()');
         $this->parser = $parser;
     }
 
@@ -418,11 +443,15 @@ class SSViewer implements Flushable
      * Returns the parser that is set for template generation
      *
      * @return TemplateParser
+     * @deprecated 5.4.0 Will be replaced with SilverStripe\View\SSTemplateEngine::getParser()
      */
     public function getParser()
     {
+        Deprecation::notice('5.4.0', 'Will be replaced with SilverStripe\View\SSTemplateEngine::getParser()');
         if (!$this->parser) {
-            $this->setParser(Injector::inst()->get('SilverStripe\\View\\SSTemplateParser'));
+            Deprecation::withSuppressedNotice(
+                fn() => $this->setParser(Injector::inst()->get('SilverStripe\\View\\SSTemplateParser'))
+            );
         }
         return $this->parser;
     }
@@ -433,10 +462,14 @@ class SSViewer implements Flushable
      * @param array|string $templates
      *
      * @return bool
+     * @deprecated 5.4.0 Will be replaced with SilverStripe\View\SSTemplateEngine::hasTemplate()
      */
     public static function hasTemplate($templates)
     {
-        return (bool)ThemeResourceLoader::inst()->findTemplate($templates, SSViewer::get_themes());
+        Deprecation::notice('5.4.0', 'Will be replaced with SilverStripe\View\SSTemplateEngine::hasTemplate()');
+        return Deprecation::withSuppressedNotice(
+            fn() => (bool)ThemeResourceLoader::inst()->findTemplate($templates, SSViewer::get_themes())
+        );
     }
 
     /**
@@ -452,9 +485,11 @@ class SSViewer implements Flushable
 
     /**
      * @return string
+     * @deprecated 5.4.0 Will be removed without equivalent functionality to replace it
      */
     public function exists()
     {
+        Deprecation::notice('5.4.0', 'Will be removed without equivalent functionality to replace it');
         return $this->chosen;
     }
 
@@ -462,10 +497,14 @@ class SSViewer implements Flushable
      * @param string $identifier A template name without '.ss' extension or path
      * @param string $type The template type, either "main", "Includes" or "Layout"
      * @return string Full system path to a template file
+     * @deprecated 5.4.0 Will be removed without equivalent functionality to replace it
      */
     public static function getTemplateFileByType($identifier, $type = null)
     {
-        return ThemeResourceLoader::inst()->findTemplate(['type' => $type, $identifier], SSViewer::get_themes());
+        Deprecation::notice('5.4.0', 'Will be removed without equivalent functionality to replace it');
+        return Deprecation::withSuppressedNotice(
+            fn() => ThemeResourceLoader::inst()->findTemplate(['type' => $type, $identifier], SSViewer::get_themes())
+        );
     }
 
     /**
@@ -475,9 +514,11 @@ class SSViewer implements Flushable
      *
      * @param bool $force Set this to true to force a re-flush. If left to false, flushing
      * may only be performed once a request.
+     * @deprecated 5.4.0 Will be replaced with SilverStripe\View\SSTemplateEngine::flushTemplateCache()
      */
     public static function flush_template_cache($force = false)
     {
+        Deprecation::notice('5.4.0', 'Will be replaced with SilverStripe\View\SSTemplateEngine::flushTemplateCache()');
         if (!SSViewer::$template_cache_flushed || $force) {
             $dir = dir(TEMP_PATH);
             while (false !== ($file = $dir->read())) {
@@ -496,9 +537,11 @@ class SSViewer implements Flushable
      *
      * @param bool $force Set this to true to force a re-flush. If left to false, flushing
      * may only be performed once a request.
+     * @deprecated 5.4.0 Will be replaced with SilverStripe\View\SSTemplateEngine::flushCacheBlockCache()
      */
     public static function flush_cacheblock_cache($force = false)
     {
+        Deprecation::notice('5.4.0', 'Will be replaced with SilverStripe\View\SSTemplateEngine::flushCacheBlockCache()');
         if (!SSViewer::$cacheblock_cache_flushed || $force) {
             $cache = Injector::inst()->get(CacheInterface::class . '.cacheblock');
             $cache->clear();
@@ -512,9 +555,11 @@ class SSViewer implements Flushable
      * Set the cache object to use when storing / retrieving partial cache blocks.
      *
      * @param CacheInterface $cache
+     * @deprecated 5.4.0 Will be replaced with SilverStripe\View\SSTemplateEngine::setPartialCacheStore()
      */
     public function setPartialCacheStore($cache)
     {
+        Deprecation::notice('5.4.0', 'Will be replaced with SilverStripe\View\SSTemplateEngine::setPartialCacheStore()');
         $this->partialCacheStore = $cache;
     }
 
@@ -522,9 +567,11 @@ class SSViewer implements Flushable
      * Get the cache object to use when storing / retrieving partial cache blocks.
      *
      * @return CacheInterface
+     * @deprecated 5.4.0 Will be replaced with SilverStripe\View\SSTemplateEngine::getPartialCacheStore()
      */
     public function getPartialCacheStore()
     {
+        Deprecation::notice('5.4.0', 'Will be replaced with SilverStripe\View\SSTemplateEngine::getPartialCacheStore()');
         if ($this->partialCacheStore) {
             return $this->partialCacheStore;
         }
@@ -552,11 +599,13 @@ class SSViewer implements Flushable
      * @param ViewableData $item The item to use as the root scope for the template
      * @param array $overlay Any variables to layer on top of the scope
      * @param array $underlay Any variables to layer underneath the scope
-     * @param ViewableData $inheritedScope The current scope of a parent template including a sub-template
+     * @param SSViewer_Scope|null $inheritedScope The current scope of a parent template including a sub-template
      * @return string The result of executing the template
+     * @deprecated 5.4.0 Will be replaced with SilverStripe\View\SSTemplateEngine::includeGeneratedTemplate()
      */
     protected function includeGeneratedTemplate($cacheFile, $item, $overlay, $underlay, $inheritedScope = null)
     {
+        Deprecation::notice('5.4.0', 'Will be replaced with SilverStripe\View\SSTemplateEngine::includeGeneratedTemplate()');
         if (isset($_GET['showtemplate']) && $_GET['showtemplate'] && Permission::check('ADMIN')) {
             $lines = file($cacheFile ?? '');
             echo "<h2>Template: $cacheFile</h2>";
@@ -567,8 +616,10 @@ class SSViewer implements Flushable
             echo "</pre>";
         }
 
-        $cache = $this->getPartialCacheStore();
-        $scope = new SSViewer_DataPresenter($item, $overlay, $underlay, $inheritedScope);
+        $cache = Deprecation::withSuppressedNotice(fn() => $this->getPartialCacheStore());
+        $scope = Deprecation::withSuppressedNotice(
+            fn() => new SSViewer_DataPresenter($item, $overlay, $underlay, $inheritedScope)
+        );
         $val = '';
 
         // Placeholder for values exposed to $cacheFile
@@ -596,6 +647,11 @@ class SSViewer implements Flushable
      */
     public function process($item, $arguments = null, $inheritedScope = null)
     {
+        if ($inheritedScope !== null) {
+            Deprecation::withSuppressedNotice(
+                fn() => Deprecation::notice('5.4.0', 'The $inheritedScope parameter is deprecated and will be removed')
+            );
+        }
         // Set hashlinks and temporarily modify global state
         $rewrite = $this->getRewriteHashLinks();
         $origRewriteDefault = static::getRewriteHashLinksDefault();
@@ -611,7 +667,7 @@ class SSViewer implements Flushable
 
         if (!file_exists($cacheFile ?? '') || filemtime($cacheFile ?? '') < $lastEdited) {
             $content = file_get_contents($template ?? '');
-            $content = $this->parseTemplateContent($content, $template);
+            $content = Deprecation::withSuppressedNotice(fn() => $this->parseTemplateContent($content, $template));
 
             $fh = fopen($cacheFile ?? '', 'w');
             fwrite($fh, $content ?? '');
@@ -624,7 +680,7 @@ class SSViewer implements Flushable
         // through $Content and $Layout placeholders.
         foreach (['Content', 'Layout'] as $subtemplate) {
             // Detect sub-template to use
-            $sub = $this->getSubtemplateFor($subtemplate);
+            $sub = Deprecation::withSuppressedNotice(fn() => $this->getSubtemplateFor($subtemplate));
             if (!$sub) {
                 continue;
             }
@@ -635,17 +691,19 @@ class SSViewer implements Flushable
                 // Disable requirements - this will be handled by the parent template
                 $subtemplateViewer->includeRequirements(false);
                 // Select the right template
-                $subtemplateViewer->setTemplate($sub);
+                Deprecation::withSuppressedNotice(fn() => $subtemplateViewer->setTemplate($sub));
 
                 // Render if available
-                if ($subtemplateViewer->exists()) {
+                if (Deprecation::withSuppressedNotice(fn() => $subtemplateViewer->exists())) {
                     return $subtemplateViewer->process($item, $arguments);
                 }
                 return null;
             };
         }
 
-        $output = $this->includeGeneratedTemplate($cacheFile, $item, $arguments, $underlay, $inheritedScope);
+        $output = Deprecation::withSuppressedNotice(
+            fn() => $this->includeGeneratedTemplate($cacheFile, $item, $arguments, $underlay, $inheritedScope)
+        );
 
         if ($this->includeRequirements) {
             $output = Requirements::includeInHTML($output);
@@ -682,9 +740,11 @@ PHP;
      * @param string $subtemplate Sub-template to use
      *
      * @return array|null
+     * @deprecated 5.4.0 Will be replaced with SilverStripe\View\SSTemplateEngine::getSubtemplateFor()
      */
     protected function getSubtemplateFor($subtemplate)
     {
+        Deprecation::notice('5.4.0', 'Will be replaced with SilverStripe\View\SSTemplateEngine::getSubtemplateFor()');
         // Get explicit subtemplate name
         if (isset($this->subTemplates[$subtemplate])) {
             return $this->subTemplates[$subtemplate];
@@ -722,9 +782,14 @@ PHP;
      * @param bool $globalRequirements
      *
      * @return string Evaluated result
+     * @deprecated 5.4.0 Will be replaced with SilverStripe\View\SSTemplateEngine::execute_template()
      */
     public static function execute_template($template, $data, $arguments = null, $scope = null, $globalRequirements = false)
     {
+        Deprecation::withSuppressedNotice(fn() => Deprecation::notice(
+            '5.4.0',
+            'Will be replaced with SilverStripe\View\SSTemplateEngine::execute_template()'
+        ));
         $v = SSViewer::create($template);
 
         if ($globalRequirements) {
@@ -754,10 +819,12 @@ PHP;
      * @param bool $globalRequirements
      *
      * @return string Evaluated result
+     * @deprecated 5.4.0 Will be replaced with SilverStripe\View\SSTemplateEngine::renderString()
      */
     public static function execute_string($content, $data, $arguments = null, $globalRequirements = false)
     {
-        $v = SSViewer::fromString($content);
+        Deprecation::notice('5.4.0', 'Will be replaced with SilverStripe\View\SSTemplateEngine::renderString()');
+        $v = Deprecation::withSuppressedNotice(fn() => SSViewer::fromString($content));
 
         if ($globalRequirements) {
             $v->includeRequirements(false);
@@ -781,9 +848,11 @@ PHP;
      * @param string $content The template contents
      * @param string $template The template file name
      * @return string
+     * @deprecated 5.4.0 Will be replaced with SilverStripe\View\SSTemplateEngine::parseTemplateContent()
      */
     public function parseTemplateContent($content, $template = "")
     {
+        Deprecation::notice('5.4.0', 'Will be replaced with SilverStripe\View\SSTemplateEngine::parseTemplateContent()');
         return $this->getParser()->compileString(
             $content,
             $template,
@@ -796,18 +865,22 @@ PHP;
      * 'Content' & 'Layout', and will have to contain 'main'
      *
      * @return array
+     * @deprecated 5.4.0 Will be removed without equivalent functionality to replace it
      */
     public function templates()
     {
+        Deprecation::notice('5.4.0', 'Will be removed without equivalent functionality to replace it');
         return array_merge(['main' => $this->chosen], $this->subTemplates);
     }
 
     /**
      * @param string $type "Layout" or "main"
      * @param string $file Full system path to the template file
+     * @deprecated 5.4.0 Will be removed without equivalent functionality to replace it
      */
     public function setTemplateFile($type, $file)
     {
+        Deprecation::notice('5.4.0', 'Will be removed without equivalent functionality to replace it');
         if (!$type || $type == 'main') {
             $this->chosen = $file;
         } else {
@@ -822,17 +895,29 @@ PHP;
      * @param string $contentGeneratedSoFar The content of the template generated so far; it should contain
      * the DOCTYPE declaration.
      * @return string
+     * @deprecated 5.4.0 Use getBaseTag() instead
      */
     public static function get_base_tag($contentGeneratedSoFar)
+    {
+        Deprecation::withSuppressedNotice(fn() => Deprecation::notice('5.4.0', 'Use getBaseTag() instead'));
+        // Is the document XHTML?
+        $isXhtml = preg_match('/<!DOCTYPE[^>]+xhtml/i', $contentGeneratedSoFar ?? '');
+        return static::getBaseTag($isXhtml);
+    }
+
+    /**
+     * Return an appropriate base tag for the given template.
+     * It will be closed on an XHTML document, and unclosed on an HTML document.
+     *
+     * @param bool $isXhtml Whether the DOCTYPE is xhtml or not.
+     */
+    public static function getBaseTag(bool $isXhtml = false): string
     {
         // Base href should always have a trailing slash
         $base = rtrim(Director::absoluteBaseURL(), '/') . '/';
-
-        // Is the document XHTML?
-        if (preg_match('/<!DOCTYPE[^>]+xhtml/i', $contentGeneratedSoFar ?? '')) {
+        if ($isXhtml) {
             return "<base href=\"$base\" />";
-        } else {
-            return "<base href=\"$base\"><!--[if lte IE 6]></base><![endif]-->";
         }
+        return "<base href=\"$base\"><!--[if lte IE 6]></base><![endif]-->";
     }
 }
diff --git a/src/View/SSViewer_DataPresenter.php b/src/View/SSViewer_DataPresenter.php
index 7c5b6e5ec..a4e82cbad 100644
--- a/src/View/SSViewer_DataPresenter.php
+++ b/src/View/SSViewer_DataPresenter.php
@@ -4,6 +4,7 @@ namespace SilverStripe\View;
 
 use InvalidArgumentException;
 use SilverStripe\Core\ClassInfo;
+use SilverStripe\Dev\Deprecation;
 use SilverStripe\ORM\FieldType\DBField;
 
 /**
@@ -11,7 +12,7 @@ use SilverStripe\ORM\FieldType\DBField;
  * data that is scope-independant (like BaseURL), or type-specific data that is layered on top cross-cut like
  * (like $FirstLast etc).
  *
- * It's separate from SSViewer_Scope to keep that fairly complex code as clean as possible.
+ * @deprecated 5.4.0 Will be merged into SilverStripe\View\SSViewer_Scope
  */
 class SSViewer_DataPresenter extends SSViewer_Scope
 {
@@ -65,6 +66,7 @@ class SSViewer_DataPresenter extends SSViewer_Scope
         array $underlay = null,
         SSViewer_Scope $inheritedScope = null
     ) {
+        Deprecation::notice('5.4.0', 'Will be merged into ' . SSViewer_Scope::class, Deprecation::SCOPE_CLASS);
         parent::__construct($item, $inheritedScope);
 
         $this->overlay = $overlay ?: [];
diff --git a/src/View/SSViewer_FromString.php b/src/View/SSViewer_FromString.php
index 40dfed6a0..6ee92403b 100644
--- a/src/View/SSViewer_FromString.php
+++ b/src/View/SSViewer_FromString.php
@@ -3,9 +3,11 @@
 namespace SilverStripe\View;
 
 use SilverStripe\Core\Config\Config;
+use SilverStripe\Dev\Deprecation;
 
 /**
  * Special SSViewer that will process a template passed as a string, rather than a filename.
+ * @deprecated 5.4.0 Will be replaced with SilverStripe\View\SSTemplateEngine::renderString()
  */
 class SSViewer_FromString extends SSViewer
 {
@@ -37,8 +39,13 @@ class SSViewer_FromString extends SSViewer
      */
     public function __construct($content, TemplateParser $parser = null)
     {
+        Deprecation::notice(
+            '5.4.0',
+            'Will be replaced with SilverStripe\View\SSTemplateEngine::renderString()',
+            Deprecation::SCOPE_CLASS
+        );
         if ($parser) {
-            $this->setParser($parser);
+            Deprecation::withSuppressedNotice(fn() => $this->setParser($parser));
         }
 
         $this->content = $content;
@@ -53,13 +60,17 @@ class SSViewer_FromString extends SSViewer
         $cacheFile = TEMP_PATH . DIRECTORY_SEPARATOR . ".cache.$hash";
 
         if (!file_exists($cacheFile ?? '') || isset($_GET['flush'])) {
-            $content = $this->parseTemplateContent($this->content, "string sha1=$hash");
+            $content = Deprecation::withSuppressedNotice(
+                fn() => $this->parseTemplateContent($this->content, "string sha1=$hash")
+            );
             $fh = fopen($cacheFile ?? '', 'w');
             fwrite($fh, $content ?? '');
             fclose($fh);
         }
 
-        $val = $this->includeGeneratedTemplate($cacheFile, $item, $arguments, null, $scope);
+        $val = Deprecation::withSuppressedNotice(
+            fn() => $this->includeGeneratedTemplate($cacheFile, $item, $arguments, null, $scope)
+        );
 
         if ($this->cacheTemplate !== null) {
             $cacheTemplate = $this->cacheTemplate;
diff --git a/src/View/SSViewer_Scope.php b/src/View/SSViewer_Scope.php
index 15a674477..6af57b035 100644
--- a/src/View/SSViewer_Scope.php
+++ b/src/View/SSViewer_Scope.php
@@ -5,6 +5,7 @@ namespace SilverStripe\View;
 use ArrayIterator;
 use Countable;
 use Iterator;
+use SilverStripe\Dev\Deprecation;
 use SilverStripe\ORM\FieldType\DBBoolean;
 use SilverStripe\ORM\FieldType\DBText;
 use SilverStripe\ORM\FieldType\DBFloat;
@@ -123,9 +124,11 @@ class SSViewer_Scope
      * Returns the current "active" item
      *
      * @return object
+     * @deprecated 5.4.0 use getCurrentItem() instead.
      */
     public function getItem()
     {
+        Deprecation::notice('5.4.0', 'use getCurrentItem() instead.');
         $item = $this->itemIterator ? $this->itemIterator->current() : $this->item;
         if (is_scalar($item)) {
             $item = $this->convertScalarToDBField($item);
@@ -133,6 +136,11 @@ class SSViewer_Scope
         return $item;
     }
 
+    public function getCurrentItem()
+    {
+        return Deprecation::withSuppressedNotice(fn() => $this->getItem());
+    }
+
     /**
      * Called at the start of every lookup chain by SSTemplateParser to indicate a new lookup from local scope
      *
@@ -185,7 +193,7 @@ class SSViewer_Scope
      */
     public function getObj($name, $arguments = [], $cache = false, $cacheName = null)
     {
-        $on = $this->getItem();
+        $on = $this->getCurrentItem();
         if ($on === null) {
             return null;
         }
@@ -198,9 +206,13 @@ class SSViewer_Scope
      * @param bool $cache
      * @param string $cacheName
      * @return $this
+     * @deprecated 5.4.0 Will be renamed scopeToIntermediateValue()
      */
     public function obj($name, $arguments = [], $cache = false, $cacheName = null)
     {
+        Deprecation::withSuppressedNotice(
+            fn() => Deprecation::notice('5.4.0', 'Will be renamed scopeToIntermediateValue()')
+        );
         switch ($name) {
             case 'Up':
                 if ($this->upIndex === null) {
@@ -252,7 +264,7 @@ class SSViewer_Scope
      */
     public function self()
     {
-        $result = $this->getItem();
+        $result = $this->getCurrentItem();
         $this->resetLocalScope();
 
         return $result;
@@ -350,8 +362,12 @@ class SSViewer_Scope
      */
     public function __call($name, $arguments)
     {
-        $on = $this->getItem();
-        $retval = $on ? $on->$name(...$arguments) : null;
+        $on = $this->getCurrentItem();
+        if ($on instanceof ViewableData && $name === 'XML_val') {
+            $retval = Deprecation::withSuppressedNotice(fn() => $on->XML_val(...$arguments));
+        } else {
+            $retval = $on ? $on->$name(...$arguments) : null;
+        }
 
         $this->resetLocalScope();
         return $retval;
diff --git a/src/View/ThemeResourceLoader.php b/src/View/ThemeResourceLoader.php
index 8799fe13a..30f560e05 100644
--- a/src/View/ThemeResourceLoader.php
+++ b/src/View/ThemeResourceLoader.php
@@ -9,6 +9,7 @@ use SilverStripe\Core\Injector\Injector;
 use SilverStripe\Core\Manifest\ModuleLoader;
 use SilverStripe\Core\Manifest\ModuleResourceLoader;
 use SilverStripe\Core\Path;
+use SilverStripe\Dev\Deprecation;
 
 /**
  * Handles finding templates from a stack of template manifest objects.
@@ -182,9 +183,11 @@ class ThemeResourceLoader implements Flushable, TemplateGlobalProvider
      * @return string Absolute path to resolved template file, or null if not resolved.
      * File location will be in the format themes/<theme>/templates/<directories>/<type>/<basename>.ss
      * Note that type (e.g. 'Layout') is not the root level directory under 'templates'.
+     * @deprecated 5.4.0 Will be removed without equivalent functionality to replace it.
      */
     public function findTemplate($template, $themes = null)
     {
+        Deprecation::notice('5.4.0', 'Will be removed without equivalent functionality to replace it.');
         if ($themes === null) {
             $themes = SSViewer::get_themes();
         }
@@ -211,7 +214,7 @@ class ThemeResourceLoader implements Flushable, TemplateGlobalProvider
         foreach ($templateList as $i => $template) {
             // Check if passed list of templates in array format
             if (is_array($template)) {
-                $path = $this->findTemplate($template, $themes);
+                $path = Deprecation::withSuppressedNotice(fn() => $this->findTemplate($template, $themes));
                 if ($path) {
                     $this->getCache()->set($cacheKey, $path);
                     return $path;
diff --git a/src/View/ViewableData.php b/src/View/ViewableData.php
index 080edcea8..51ed3e973 100644
--- a/src/View/ViewableData.php
+++ b/src/View/ViewableData.php
@@ -426,9 +426,11 @@ class ViewableData implements IteratorAggregate
      *
      * @param string $field
      * @return string
+     * @deprecated 5.4.0 Will be removed without equivalent functionality to replace it.
      */
     public function castingClass($field)
     {
+        Deprecation::notice('5.4.0', 'Will be removed without equivalent functionality to replace it.');
         // Strip arguments
         $spec = $this->castingHelper($field);
         return trim(strtok($spec ?? '', '(') ?? '');
@@ -439,10 +441,13 @@ class ViewableData implements IteratorAggregate
      *
      * @param string $field
      * @return string 'xml'|'raw'
+     * @deprecated 5.4.0 Will be removed without equivalent functionality to replace it.
      */
     public function escapeTypeForField($field)
     {
-        $class = $this->castingClass($field) ?: $this->config()->get('default_cast');
+        Deprecation::notice('5.4.0', 'Will be removed without equivalent functionality to replace it.');
+        $class = Deprecation::withSuppressedNotice(fn() => $this->castingClass($field))
+            ?: $this->config()->get('default_cast');
 
         /** @var DBField $type */
         $type = Injector::inst()->get($class, true);
@@ -488,9 +493,11 @@ class ViewableData implements IteratorAggregate
      * @param string $fieldName Name of field
      * @param array $arguments List of optional arguments given
      * @return string
+     * @deprecated 5.4.0 Will be made private
      */
     protected function objCacheName($fieldName, $arguments)
     {
+        Deprecation::notice('5.4.0', 'Will be made private');
         return $arguments
             ? $fieldName . ":" . var_export($arguments, true)
             : $fieldName;
@@ -546,8 +553,11 @@ class ViewableData implements IteratorAggregate
      */
     public function obj($fieldName, $arguments = [], $cache = false, $cacheName = null)
     {
+        if ($cacheName !== null) {
+            Deprecation::notice('5.4.0', 'The $cacheName parameter has been deprecated and will be removed');
+        }
         if (!$cacheName && $cache) {
-            $cacheName = $this->objCacheName($fieldName, $arguments);
+            $cacheName = Deprecation::withSuppressedNotice(fn() => $this->objCacheName($fieldName, $arguments));
         }
 
         // Check pre-cached value
@@ -588,9 +598,11 @@ class ViewableData implements IteratorAggregate
      * @param array $arguments
      * @param string $identifier an optional custom cache identifier
      * @return Object|DBField
+     * @deprecated 5.4.0 use obj() instead
      */
     public function cachedCall($fieldName, $arguments = [], $identifier = null)
     {
+        Deprecation::notice('5.4.0', 'Use obj() instead');
         return $this->obj($fieldName, $arguments, true, $identifier);
     }
 
@@ -617,9 +629,11 @@ class ViewableData implements IteratorAggregate
      * @param array $arguments
      * @param bool $cache
      * @return string
+     * @deprecated 5.4.0 Will be removed without equivalent functionality to replace it
      */
     public function XML_val($field, $arguments = [], $cache = false)
     {
+        Deprecation::notice('5.4.0', 'Will be removed without equivalent functionality to replace it');
         $result = $this->obj($field, $arguments, $cache);
         // Might contain additional formatting over ->XML(). E.g. parse shortcodes, nl2br()
         return $result->forTemplate();
@@ -630,13 +644,14 @@ class ViewableData implements IteratorAggregate
      *
      * @param array $fields an array of field names
      * @return array
+     * @deprecated 5.4.0 Will be removed without equivalent functionality to replace it
      */
     public function getXMLValues($fields)
     {
         $result = [];
 
         foreach ($fields as $field) {
-            $result[$field] = $this->XML_val($field);
+            $result[$field] = Deprecation::withSuppressedNotice(fn() => $this->XML_val($field));
         }
 
         return $result;
diff --git a/tests/php/Core/Manifest/ThemeResourceLoaderTest.php b/tests/php/Core/Manifest/ThemeResourceLoaderTest.php
index 0c4c424f7..c96c58af0 100644
--- a/tests/php/Core/Manifest/ThemeResourceLoaderTest.php
+++ b/tests/php/Core/Manifest/ThemeResourceLoaderTest.php
@@ -9,6 +9,7 @@ use SilverStripe\View\ThemeResourceLoader;
 use SilverStripe\View\ThemeManifest;
 use SilverStripe\Dev\SapphireTest;
 use SilverStripe\Core\Manifest\ModuleManifest;
+use SilverStripe\Dev\Deprecation;
 
 /**
  * Tests for the {@link TemplateLoader} class.
@@ -73,41 +74,46 @@ class ThemeResourceLoaderTest extends SapphireTest
     {
         $this->assertEquals(
             "$this->base/module/templates/Page.ss",
-            $this->loader->findTemplate('Page', ['$default'])
+            Deprecation::withSuppressedNotice(fn() => $this->loader->findTemplate('Page', ['$default']))
         );
 
         $this->assertEquals(
             "$this->base/module/templates/Layout/Page.ss",
-            $this->loader->findTemplate(['type' => 'Layout', 'Page'], ['$default'])
+            Deprecation::withSuppressedNotice(
+                fn() => $this->loader->findTemplate(['type' => 'Layout', 'Page'], ['$default'])
+            )
         );
     }
 
     public function testFindNestedThemeTemplates()
     {
         // Without including the theme this template cannot be found
-        $this->assertEquals(null, $this->loader->findTemplate('NestedThemePage', ['$default']));
+        $this->assertEquals(
+            null,
+            Deprecation::withSuppressedNotice(fn() => $this->loader->findTemplate('NestedThemePage', ['$default']))
+        );
 
         // With a nested theme available then it is available
         $this->assertEquals(
             "{$this->base}/module/themes/subtheme/templates/NestedThemePage.ss",
-            $this->loader->findTemplate(
+            Deprecation::withSuppressedNotice(fn() => $this->loader->findTemplate(
                 'NestedThemePage',
                 [
                     'silverstripe/module:subtheme',
                     '$default'
                 ]
-            )
+            ))
         );
 
         // Can also be found if excluding $default theme
         $this->assertEquals(
             "{$this->base}/module/themes/subtheme/templates/NestedThemePage.ss",
-            $this->loader->findTemplate(
+            Deprecation::withSuppressedNotice(fn() => $this->loader->findTemplate(
                 'NestedThemePage',
                 [
                     'silverstripe/module:subtheme',
                 ]
-            )
+            ))
         );
     }
 
@@ -116,7 +122,7 @@ class ThemeResourceLoaderTest extends SapphireTest
         // Test that "type" is respected properly
         $this->assertEquals(
             "{$this->base}/module/templates/MyNamespace/Layout/MyClass.ss",
-            $this->loader->findTemplate(
+            Deprecation::withSuppressedNotice(fn() => $this->loader->findTemplate(
                 [
                     [
                         'type' => 'Layout',
@@ -133,13 +139,13 @@ class ThemeResourceLoaderTest extends SapphireTest
                     'theme',
                     '$default',
                 ]
-            )
+            ))
         );
 
         // Non-typed template can be found even if looking for typed theme at a lower priority
         $this->assertEquals(
             "{$this->base}/module/templates/MyNamespace/MyClass.ss",
-            $this->loader->findTemplate(
+            Deprecation::withSuppressedNotice(fn() => $this->loader->findTemplate(
                 [
                     [
                         'type' => 'Layout',
@@ -156,7 +162,7 @@ class ThemeResourceLoaderTest extends SapphireTest
                     'theme',
                     '$default',
                 ]
-            )
+            ))
         );
     }
 
@@ -165,30 +171,32 @@ class ThemeResourceLoaderTest extends SapphireTest
         // Items given as full paths are returned directly
         $this->assertEquals(
             "$this->base/themes/theme/templates/Page.ss",
-            $this->loader->findTemplate("$this->base/themes/theme/templates/Page.ss", ['theme'])
+            Deprecation::withSuppressedNotice(
+                fn() => $this->loader->findTemplate("$this->base/themes/theme/templates/Page.ss", ['theme'])
+            )
         );
 
         $this->assertEquals(
             "$this->base/themes/theme/templates/Page.ss",
-            $this->loader->findTemplate(
+            Deprecation::withSuppressedNotice(fn() => $this->loader->findTemplate(
                 [
                     "$this->base/themes/theme/templates/Page.ss",
                     "Page"
                 ],
                 ['theme']
-            )
+            ))
         );
 
         // Ensure checks for file_exists
         $this->assertEquals(
             "$this->base/themes/theme/templates/Page.ss",
-            $this->loader->findTemplate(
+            Deprecation::withSuppressedNotice(fn() => $this->loader->findTemplate(
                 [
                     "$this->base/themes/theme/templates/NotAPage.ss",
                     "$this->base/themes/theme/templates/Page.ss",
                 ],
                 ['theme']
-            )
+            ))
         );
     }
 
@@ -199,12 +207,14 @@ class ThemeResourceLoaderTest extends SapphireTest
     {
         $this->assertEquals(
             "$this->base/themes/theme/templates/Page.ss",
-            $this->loader->findTemplate('Page', ['theme'])
+            Deprecation::withSuppressedNotice(fn() => $this->loader->findTemplate('Page', ['theme']))
         );
 
         $this->assertEquals(
             "$this->base/themes/theme/templates/Layout/Page.ss",
-            $this->loader->findTemplate(['type' => 'Layout', 'Page'], ['theme'])
+            Deprecation::withSuppressedNotice(
+                fn() => $this->loader->findTemplate(['type' => 'Layout', 'Page'], ['theme'])
+            )
         );
     }
 
@@ -221,12 +231,14 @@ class ThemeResourceLoaderTest extends SapphireTest
 
         $this->assertEquals(
             "$this->base/myproject/templates/Page.ss",
-            $this->loader->findTemplate('Page', ['$default'])
+            Deprecation::withSuppressedNotice(fn() => $this->loader->findTemplate('Page', ['$default']))
         );
 
         $this->assertEquals(
             "$this->base/myproject/templates/Layout/Page.ss",
-            $this->loader->findTemplate(['type' => 'Layout', 'Page'], ['$default'])
+            Deprecation::withSuppressedNotice(
+                fn() => $this->loader->findTemplate(['type' => 'Layout', 'Page'], ['$default'])
+            )
         );
 
         $this->removeTestTemplates($templates);
@@ -239,12 +251,16 @@ class ThemeResourceLoaderTest extends SapphireTest
     {
         $this->assertEquals(
             "$this->base/themes/theme/templates/CustomThemePage.ss",
-            $this->loader->findTemplate('CustomThemePage', ['theme', '$default'])
+            Deprecation::withSuppressedNotice(
+                fn() => $this->loader->findTemplate('CustomThemePage', ['theme', '$default'])
+            )
         );
 
         $this->assertEquals(
             "$this->base/module/templates/Layout/CustomThemePage.ss",
-            $this->loader->findTemplate(['type' => 'Layout', 'CustomThemePage'], ['theme', '$default'])
+            Deprecation::withSuppressedNotice(
+                fn() => $this->loader->findTemplate(['type' => 'Layout', 'CustomThemePage'], ['theme', '$default'])
+            )
         );
     }
 
@@ -390,7 +406,7 @@ class ThemeResourceLoaderTest extends SapphireTest
 
         $loader = new ThemeResourceLoader();
         $loader->setCache($mockCache);
-        $loader->findTemplate('Page', ['$default']);
+        Deprecation::withSuppressedNotice(fn() => $loader->findTemplate('Page', ['$default']));
     }
 
     public function testFindTemplateWithCacheHit()
@@ -402,6 +418,9 @@ class ThemeResourceLoaderTest extends SapphireTest
 
         $loader = new ThemeResourceLoader();
         $loader->setCache($mockCache);
-        $this->assertSame('mock_template.ss', $loader->findTemplate('Page', ['$default']));
+        $this->assertSame(
+            'mock_template.ss',
+            Deprecation::withSuppressedNotice(fn() => $loader->findTemplate('Page', ['$default']))
+        );
     }
 }
diff --git a/tests/php/View/ContentNegotiatorTest.php b/tests/php/View/ContentNegotiatorTest.php
index 7465e55fa..ec2fdf602 100644
--- a/tests/php/View/ContentNegotiatorTest.php
+++ b/tests/php/View/ContentNegotiatorTest.php
@@ -5,6 +5,7 @@ namespace SilverStripe\View\Tests;
 use SilverStripe\Dev\SapphireTest;
 use SilverStripe\Control\ContentNegotiator;
 use SilverStripe\Control\HTTPResponse;
+use SilverStripe\Dev\Deprecation;
 use SilverStripe\View\SSViewer;
 use SilverStripe\View\Tests\SSViewerTest\TestFixture;
 
@@ -17,7 +18,7 @@ class ContentNegotiatorTest extends SapphireTest
      */
     private function render($templateString, $data = null)
     {
-        $t = SSViewer::fromString($templateString);
+        $t = Deprecation::withSuppressedNotice(fn() => SSViewer::fromString($templateString));
         if (!$data) {
             $data = new TestFixture();
         }
diff --git a/tests/php/View/SSViewerCacheBlockTest.php b/tests/php/View/SSViewerCacheBlockTest.php
index 09f334884..931ca51a4 100644
--- a/tests/php/View/SSViewerCacheBlockTest.php
+++ b/tests/php/View/SSViewerCacheBlockTest.php
@@ -9,6 +9,7 @@ use SilverStripe\Versioned\Versioned;
 use Psr\SimpleCache\CacheInterface;
 use SilverStripe\Dev\SapphireTest;
 use SilverStripe\Control\Director;
+use SilverStripe\Dev\Deprecation;
 use SilverStripe\View\SSTemplateParseException;
 use SilverStripe\View\SSViewer;
 use Symfony\Component\Cache\Adapter\FilesystemAdapter;
@@ -64,7 +65,7 @@ class SSViewerCacheBlockTest extends SapphireTest
             $data = $this->data->customise($data);
         }
 
-        return SSViewer::execute_string($template, $data);
+        return Deprecation::withSuppressedNotice(fn() => SSViewer::execute_string($template, $data));
     }
 
     public function testParsing()
@@ -177,13 +178,13 @@ class SSViewerCacheBlockTest extends SapphireTest
         $data->setEntropy('default');
         $this->assertEquals(
             'default Stage.Stage',
-            SSViewer::execute_string('<% cached %>$Inspect<% end_cached %>', $data)
+            Deprecation::withSuppressedNotice(fn() => SSViewer::execute_string('<% cached %>$Inspect<% end_cached %>', $data))
         );
         $data = new SSViewerCacheBlockTest\VersionedModel();
         $data->setEntropy('first');
         $this->assertEquals(
             'first Stage.Stage',
-            SSViewer::execute_string('<% cached %>$Inspect<% end_cached %>', $data)
+            Deprecation::withSuppressedNotice(fn() => SSViewer::execute_string('<% cached %>$Inspect<% end_cached %>', $data))
         );
 
         // Run without caching in live to prove data is uncached
diff --git a/tests/php/View/SSViewerTest.php b/tests/php/View/SSViewerTest.php
index 3b55fa9d9..2b06e8e55 100644
--- a/tests/php/View/SSViewerTest.php
+++ b/tests/php/View/SSViewerTest.php
@@ -13,6 +13,7 @@ use SilverStripe\Control\Director;
 use SilverStripe\Control\HTTPResponse;
 use SilverStripe\Core\Convert;
 use SilverStripe\Core\Injector\Injector;
+use SilverStripe\Dev\Deprecation;
 use SilverStripe\Dev\SapphireTest;
 use SilverStripe\i18n\i18n;
 use SilverStripe\ORM\ArrayList;
@@ -196,7 +197,7 @@ class SSViewerTest extends SapphireTest
      */
     public function render($templateString, $data = null, $cacheTemplate = false)
     {
-        $t = SSViewer::fromString($templateString, $cacheTemplate);
+        $t = Deprecation::withSuppressedNotice(fn() => SSViewer::fromString($templateString, $cacheTemplate));
         if (!$data) {
             $data = new SSViewerTest\TestFixture();
         }
@@ -1304,29 +1305,29 @@ after'
         // Value casted as "Text"
         $this->assertEquals(
             '&lt;b&gt;html&lt;/b&gt;',
-            $t = SSViewer::fromString('$TextValue')->process($vd)
+            Deprecation::withSuppressedNotice(fn() => SSViewer::fromString('$TextValue'))->process($vd)
         );
         $this->assertEquals(
             '<b>html</b>',
-            $t = SSViewer::fromString('$TextValue.RAW')->process($vd)
+            Deprecation::withSuppressedNotice(fn() => SSViewer::fromString('$TextValue.RAW'))->process($vd)
         );
         $this->assertEquals(
             '&lt;b&gt;html&lt;/b&gt;',
-            $t = SSViewer::fromString('$TextValue.XML')->process($vd)
+            Deprecation::withSuppressedNotice(fn() => SSViewer::fromString('$TextValue.XML'))->process($vd)
         );
 
         // Value casted as "HTMLText"
         $this->assertEquals(
             '<b>html</b>',
-            $t = SSViewer::fromString('$HTMLValue')->process($vd)
+            Deprecation::withSuppressedNotice(fn() => SSViewer::fromString('$HTMLValue'))->process($vd)
         );
         $this->assertEquals(
             '<b>html</b>',
-            $t = SSViewer::fromString('$HTMLValue.RAW')->process($vd)
+            Deprecation::withSuppressedNotice(fn() => SSViewer::fromString('$HTMLValue.RAW'))->process($vd)
         );
         $this->assertEquals(
             '&lt;b&gt;html&lt;/b&gt;',
-            $t = SSViewer::fromString('$HTMLValue.XML')->process($vd)
+            Deprecation::withSuppressedNotice(fn() => SSViewer::fromString('$HTMLValue.XML'))->process($vd)
         );
 
         // Uncasted value (falls back to ViewableData::$default_cast="Text")
@@ -1334,15 +1335,15 @@ after'
         $vd->UncastedValue = '<b>html</b>';
         $this->assertEquals(
             '&lt;b&gt;html&lt;/b&gt;',
-            $t = SSViewer::fromString('$UncastedValue')->process($vd)
+            Deprecation::withSuppressedNotice(fn() => SSViewer::fromString('$UncastedValue'))->process($vd)
         );
         $this->assertEquals(
             '<b>html</b>',
-            $t = SSViewer::fromString('$UncastedValue.RAW')->process($vd)
+            Deprecation::withSuppressedNotice(fn() => SSViewer::fromString('$UncastedValue.RAW'))->process($vd)
         );
         $this->assertEquals(
             '&lt;b&gt;html&lt;/b&gt;',
-            $t = SSViewer::fromString('$UncastedValue.XML')->process($vd)
+            Deprecation::withSuppressedNotice(fn() => SSViewer::fromString('$UncastedValue.XML'))->process($vd)
         );
     }
 
@@ -2039,7 +2040,9 @@ EOC;
     public function testLoopIteratorIterator()
     {
         $list = new PaginatedList(new ArrayList());
-        $viewer = new SSViewer_FromString('<% loop List %>$ID - $FirstName<br /><% end_loop %>');
+        $viewer = Deprecation::withSuppressedNotice(
+            fn() => new SSViewer_FromString('<% loop List %>$ID - $FirstName<br /><% end_loop %>')
+        );
         $result = $viewer->process(new ArrayData(['List' => $list]));
         $this->assertEquals($result, '');
     }
@@ -2182,7 +2185,9 @@ EOC;
             }
         );
 
-        $template = new SSViewer_FromString("<% test %><% end_test %>", $parser);
+        $template = Deprecation::withSuppressedNotice(
+            fn() => new SSViewer_FromString("<% test %><% end_test %>", $parser)
+        );
         $template->process(new SSViewerTest\TestFixture());
 
         $this->assertEquals(1, $count);
@@ -2199,7 +2204,7 @@ EOC;
             }
         );
 
-        $template = new SSViewer_FromString("<% test %>", $parser);
+        $template = Deprecation::withSuppressedNotice(fn() => new SSViewer_FromString("<% test %>", $parser));
         $template->process(new SSViewerTest\TestFixture());
 
         $this->assertEquals(1, $count);
diff --git a/tests/php/View/ViewableDataTest.php b/tests/php/View/ViewableDataTest.php
index 15ff74252..983ea1a37 100644
--- a/tests/php/View/ViewableDataTest.php
+++ b/tests/php/View/ViewableDataTest.php
@@ -3,6 +3,7 @@
 namespace SilverStripe\View\Tests;
 
 use ReflectionMethod;
+use SilverStripe\Dev\Deprecation;
 use SilverStripe\ORM\FieldType\DBField;
 use SilverStripe\Dev\SapphireTest;
 use SilverStripe\View\ArrayData;
@@ -77,12 +78,12 @@ class ViewableDataTest extends SapphireTest
     {
         $caster = new ViewableDataTest\Castable();
 
-        $this->assertEquals('casted', $caster->XML_val('alwaysCasted'));
-        $this->assertEquals('casted', $caster->XML_val('noCastingInformation'));
+        $this->assertEquals('casted', Deprecation::withSuppressedNotice(fn() => $caster->XML_val('alwaysCasted')));
+        $this->assertEquals('casted', Deprecation::withSuppressedNotice(fn() => $caster->XML_val('noCastingInformation')));
 
         // Test automatic escaping is applied even to fields with no 'casting'
-        $this->assertEquals('casted', $caster->XML_val('unsafeXML'));
-        $this->assertEquals('&lt;foo&gt;', $caster->XML_val('castedUnsafeXML'));
+        $this->assertEquals('casted', Deprecation::withSuppressedNotice(fn() => $caster->XML_val('unsafeXML')));
+        $this->assertEquals('&lt;foo&gt;', Deprecation::withSuppressedNotice(fn() => $caster->XML_val('castedUnsafeXML')));
     }
 
     public function testArrayCustomise()
@@ -95,11 +96,11 @@ class ViewableDataTest extends SapphireTest
              ]
         );
 
-        $this->assertEquals('test', $viewableData->XML_val('test'));
-        $this->assertEquals('casted', $viewableData->XML_val('alwaysCasted'));
+        $this->assertEquals('test', Deprecation::withSuppressedNotice(fn() => $viewableData->XML_val('test')));
+        $this->assertEquals('casted', Deprecation::withSuppressedNotice(fn() => $viewableData->XML_val('alwaysCasted')));
 
-        $this->assertEquals('overwritten', $newViewableData->XML_val('test'));
-        $this->assertEquals('overwritten', $newViewableData->XML_val('alwaysCasted'));
+        $this->assertEquals('overwritten', Deprecation::withSuppressedNotice(fn() => $newViewableData->XML_val('test')));
+        $this->assertEquals('overwritten', Deprecation::withSuppressedNotice(fn() => $newViewableData->XML_val('alwaysCasted')));
 
         $this->assertEquals('castable', $viewableData->forTemplate());
         $this->assertEquals('castable', $newViewableData->forTemplate());
@@ -110,11 +111,11 @@ class ViewableDataTest extends SapphireTest
         $viewableData    = new ViewableDataTest\Castable();
         $newViewableData = $viewableData->customise(new ViewableDataTest\RequiresCasting());
 
-        $this->assertEquals('test', $viewableData->XML_val('test'));
-        $this->assertEquals('casted', $viewableData->XML_val('alwaysCasted'));
+        $this->assertEquals('test', Deprecation::withSuppressedNotice(fn() => $viewableData->XML_val('test')));
+        $this->assertEquals('casted', Deprecation::withSuppressedNotice(fn() => $viewableData->XML_val('alwaysCasted')));
 
-        $this->assertEquals('overwritten', $newViewableData->XML_val('test'));
-        $this->assertEquals('casted', $newViewableData->XML_val('alwaysCasted'));
+        $this->assertEquals('overwritten', Deprecation::withSuppressedNotice(fn() => $newViewableData->XML_val('test')));
+        $this->assertEquals('casted', Deprecation::withSuppressedNotice(fn() => $newViewableData->XML_val('alwaysCasted')));
 
         $this->assertEquals('castable', $viewableData->forTemplate());
         $this->assertEquals('casted', $newViewableData->forTemplate());
@@ -147,7 +148,7 @@ class ViewableDataTest extends SapphireTest
         foreach ($expected as $field => $class) {
             $this->assertEquals(
                 $class,
-                $obj->castingClass($field),
+                Deprecation::withSuppressedNotice(fn() => $obj->castingClass($field)),
                 "castingClass() returns correct results for ::\$$field"
             );
         }
@@ -159,7 +160,7 @@ class ViewableDataTest extends SapphireTest
 
         // Save a literal string into cache
         $cache = true;
-        $uncastedData = $obj->obj('noCastingInformation', null, false, $cache);
+        $uncastedData = $obj->obj('noCastingInformation', null, $cache);
 
         // Fetch the cached string as an object
         $forceReturnedObject = true;
@@ -184,15 +185,15 @@ class ViewableDataTest extends SapphireTest
         $objCached->Test = 'AAA';
         $objNotCached->Test = 'AAA';
 
-        $this->assertEquals('AAA', $objCached->obj('Test', null, true, true));
-        $this->assertEquals('AAA', $objNotCached->obj('Test', null, true, true));
+        $this->assertEquals('AAA', $objCached->obj('Test', null, true));
+        $this->assertEquals('AAA', $objNotCached->obj('Test', null, true));
 
         $objCached->Test = 'BBB';
         $objNotCached->Test = 'BBB';
 
         // Cached data must be always the same
-        $this->assertEquals('AAA', $objCached->obj('Test', null, true, true));
-        $this->assertEquals('BBB', $objNotCached->obj('Test', null, true, true));
+        $this->assertEquals('AAA', $objCached->obj('Test', null, true));
+        $this->assertEquals('BBB', $objNotCached->obj('Test', null, true));
     }
 
     public function testSetFailover()
diff --git a/tests/php/i18n/i18nTestManifest.php b/tests/php/i18n/i18nTestManifest.php
index c345a2166..b81a54ae7 100644
--- a/tests/php/i18n/i18nTestManifest.php
+++ b/tests/php/i18n/i18nTestManifest.php
@@ -8,6 +8,7 @@ use SilverStripe\Core\Manifest\ClassManifest;
 use SilverStripe\Core\Manifest\ClassLoader;
 use SilverStripe\Core\Manifest\ModuleLoader;
 use SilverStripe\Core\Manifest\ModuleManifest;
+use SilverStripe\Dev\Deprecation;
 use SilverStripe\i18n\i18n;
 use SilverStripe\i18n\Messages\MessageProvider;
 use SilverStripe\i18n\Messages\Symfony\ModuleYamlLoader;
@@ -73,7 +74,7 @@ trait i18nTestManifest
     {
         // force SSViewer_DataPresenter to cache global template vars before we switch to the
         // test-project class manifest (since it will lose visibility of core classes)
-        $presenter = new SSViewer_DataPresenter(new ViewableData());
+        $presenter = Deprecation::withSuppressedNotice(fn() => new SSViewer_DataPresenter(new ViewableData()));
         unset($presenter);
 
         // Switch to test manifest