diff --git a/admin/code/LeftAndMain.php b/admin/code/LeftAndMain.php
index 3cca23b1b..d7ff2b56b 100644
--- a/admin/code/LeftAndMain.php
+++ b/admin/code/LeftAndMain.php
@@ -266,7 +266,7 @@ class LeftAndMain extends Controller implements PermissionProvider {
 			// Use theme from the site config
 			if(class_exists('SiteConfig') && ($config = SiteConfig::current_site_config()) && $config->Theme) {
 				$theme = $config->Theme;
-			} elseif(Config::inst()->get('SSViewer', 'theme')) {
+			} elseif(Config::inst()->get('SSViewer', 'theme_enabled') && Config::inst()->get('SSViewer', 'theme')) {
 				$theme = Config::inst()->get('SSViewer', 'theme');
 			} else {
 				$theme = false;
@@ -387,9 +387,8 @@ class LeftAndMain extends Controller implements PermissionProvider {
 		$dummy = null;
 		$this->extend('init', $dummy);
 
-		// The user's theme shouldn't affect the CMS, if, for example, they have replaced
-		// TableListField.ss or Form.ss.
-		Config::inst()->update('SSViewer', 'theme', null);
+		// The user's theme shouldn't affect the CMS, if, for example, they have replaced TableListField.ss or Form.ss.
+		Config::inst()->update('SSViewer', 'theme_enabled', false);
 	}
 	
 	public function handleRequest(SS_HTTPRequest $request, DataModel $model = null) {
diff --git a/control/Director.php b/control/Director.php
index a1ef3b0e4..7f1d9f5b5 100644
--- a/control/Director.php
+++ b/control/Director.php
@@ -200,6 +200,8 @@ class Director implements TemplateGlobalProvider {
 	public static function test($url, $postVars = null, $session = null, $httpMethod = null, $body = null,
 			$headers = null, $cookies = null, &$request = null) {
 
+		Config::nest();
+
 		// These are needed so that calling Director::test() doesnt muck with whoever is calling it.
 		// Really, it's some inappropriate coupling and should be resolved by making less use of statics
 		$oldStage = Versioned::current_stage();
@@ -217,7 +219,6 @@ class Director implements TemplateGlobalProvider {
 		$existingCookies = isset($_COOKIE) ? $_COOKIE : array();
 		$existingServer	= isset($_SERVER) ? $_SERVER : array();
 		
-		$existingCookieReportErrors = Config::inst()->get('Cookie', 'report_errors');
 		$existingRequirementsBackend = Requirements::backend();
 
 		Config::inst()->update('Cookie', 'report_errors', false);
@@ -268,12 +269,13 @@ class Director implements TemplateGlobalProvider {
 		$_COOKIE = $existingCookies;
 		$_SERVER = $existingServer;
 
-		Config::inst()->update('Cookie', 'report_errors', $existingCookieReportErrors);
 		Requirements::set_backend($existingRequirementsBackend);
 
 		// These are needed so that calling Director::test() doesnt muck with whoever is calling it.
 		// Really, it's some inappropriate coupling and should be resolved by making less use of statics
 		Versioned::reading_stage($oldStage);
+
+		Config::unnest();
 		
 		return $result;
 	}
diff --git a/docs/en/changelogs/3.1.0.md b/docs/en/changelogs/3.1.0.md
index a5d27292d..4ba8abaad 100644
--- a/docs/en/changelogs/3.1.0.md
+++ b/docs/en/changelogs/3.1.0.md
@@ -427,4 +427,7 @@ you can enable those warnings and future-proof your code already.
 	 `YearlyTask` are deprecated, please extend from `BuildTask` or `CliController`,
 	 and invoke them in self-defined frequencies through Unix cronjobs etc.
  * `i18n::$common_locales` and `i18n::$common_languages` are now accessed via the Config API, and contain associative rather than indexed arrays.
-   Before: `array('de_DE' => array('German', 'Deutsch'))`, after: `array('de_DE' => array('name' => 'German', 'native' => 'Deutsch'))`.
\ No newline at end of file
+   Before: `array('de_DE' => array('German', 'Deutsch'))`, after: `array('de_DE' => array('name' => 'German', 'native' => 'Deutsch'))`. 
+ * `SSViewer::current_custom_theme()` has been replaced with the `SSViewer.theme_enabled` configuration setting.
+   Please use it to toggle theme behaviour rather than relying on the custom theme being set in the
+   (now deprecated) `SSViewer::set_theme()` call.
\ No newline at end of file
diff --git a/view/SSViewer.php b/view/SSViewer.php
index e3a4d098f..38e862d75 100644
--- a/view/SSViewer.php
+++ b/view/SSViewer.php
@@ -572,15 +572,20 @@ class SSViewer {
 	
 	/**
 	 * @config
-	 * @var string
+	 * @var string The used "theme", which usually consists of templates, images and stylesheets.
+	 * Only used when {@link $theme_enabled} is set to TRUE.
 	 */
-	private static $current_theme = null;
-	
+	private static $theme = null;
+
 	/**
 	 * @config
-	 * @var string
+	 * @var boolean Use the theme. Set to FALSE in order to disable themes,
+	 * which can be useful for scenarios where theme overrides are temporarily undesired,
+	 * such as an administrative interface separate from the website theme. 
+	 * It retains the theme settings to be re-enabled, for example when a website content
+	 * needs to be rendered from within this administrative interface.
 	 */
-	private static $current_custom_theme = null;
+	private static $theme_enabled = true;
 
 	/**
 	 * @var boolean
@@ -603,9 +608,6 @@ class SSViewer {
 	public static function set_theme($theme) {
 		Deprecation::notice('3.2', 'Use the "SSViewer.theme" config setting instead');
 		Config::inst()->update('SSViewer', 'theme', $theme);
-		//Static publishing needs to have a theme set, otherwise it defaults to the content controller theme
-		if(!is_null($theme))
-			Config::inst()->update('SSViewer', 'custom_theme', $theme);
 	}
 	
 	/**
@@ -655,8 +657,8 @@ class SSViewer {
 	 * @return string
 	 */
 	public static function current_custom_theme(){
-		Deprecation::notice('3.2', 'Use the "SSViewer.theme" config setting instead');
-		return Config::inst()->get('SSViewer', 'custom_theme');
+		Deprecation::notice('3.2', 'Use the "SSViewer.theme" and "SSViewer.theme_enabled" config settings instead');
+		return Config::inst()->get('SSViewer', 'theme_enabled') ? Config::inst()->get('SSViewer', 'theme') : null;
 	}
 	
 	/**
@@ -683,8 +685,13 @@ class SSViewer {
 		if(!is_array($templateList) && substr((string) $templateList,-3) == '.ss') {
 			$this->chosenTemplates['main'] = $templateList;
 		} else {
+			if(Config::inst()->get('SSViewer', 'theme_enabled')) {
+				$theme = Config::inst()->get('SSViewer', 'theme');
+			} else {
+				$theme = null;
+			}
 			$this->chosenTemplates = SS_TemplateLoader::instance()->findTemplates(
-				$templateList, Config::inst()->get('SSViewer', 'theme')
+				$templateList, $theme
 			);
 		}
 
@@ -792,7 +799,12 @@ class SSViewer {
 	 */
 	public static function getTemplateFileByType($identifier, $type) {
 		$loader = SS_TemplateLoader::instance();
-		$found  = $loader->findTemplates("$type/$identifier", Config::inst()->get('SSViewer', 'theme'));
+		if(Config::inst()->get('SSViewer', 'theme_enabled')) {
+			$theme = Config::inst()->get('SSViewer', 'theme');
+		} else {
+			$theme = null;
+		}
+		$found  = $loader->findTemplates("$type/$identifier", $theme);
 
 		if ($found) {
 			return $found['main'];
diff --git a/view/ViewableData.php b/view/ViewableData.php
index 895115069..7e3fcf341 100644
--- a/view/ViewableData.php
+++ b/view/ViewableData.php
@@ -522,7 +522,10 @@ class ViewableData extends Object implements IteratorAggregate {
 	 * @return string
 	 */
 	public function ThemeDir($subtheme = false) {
-		if($theme = Config::inst()->get('SSViewer', 'theme')) {
+		if(
+			Config::inst()->get('SSViewer', 'theme_enabled') 
+			&& $theme = Config::inst()->get('SSViewer', 'theme')
+		) {
 			return THEMES_DIR . "/$theme" . ($subtheme ? "_$subtheme" : null);
 		}