diff --git a/code/LeftAndMain.php b/code/LeftAndMain.php
index 90c41df2..a0247020 100644
--- a/code/LeftAndMain.php
+++ b/code/LeftAndMain.php
@@ -32,6 +32,8 @@ class LeftAndMain extends Controller {
 
 	static $tree_class = null;
 	
+	static $edit_timeout = 180;
+	
 	static $ForceReload;
 
 	static $allowed_actions = array(
@@ -48,7 +50,7 @@ class LeftAndMain extends Controller {
 		'Member_ProfileForm',
 		'EditorToolbar',
 		'EditForm',
-		
+		'pageStatus',
 	);
 	
 	/**
@@ -343,7 +345,7 @@ class LeftAndMain extends Controller {
 		}
 
 		$form = $this->EditForm();
-		if($form) return $form->formHtmlContent();
+		if ($form) return $form->formHtmlContent();
 		else return "";
 	}
 	public function getLastFormIn($html) {
@@ -716,6 +718,9 @@ JS;
 				FormResponse::add("\$('Form_EditForm_StageURLSegment').value = \"{$record->URLSegment}\";");
 			}
 
+			$newVersion = ((int)$record->Version) + 1;
+			FormResponse::add("\$('Form_EditForm_Version').value = {$newVersion};");
+			
 			// If the 'Save & Publish' button was clicked, also publish the page
 			if (isset($urlParams['publish']) && $urlParams['publish'] == 1) {
 				$record->doPublish();
@@ -971,6 +976,8 @@ JS;
 				
 				DataObject::delete_by_id($this->stat('tree_class'), $id);
 				$script .= "node = st.getTreeNodeByIdx($id); if(node) node.parentTreeNode.removeTreeNode(node); $('Form_EditForm').closeIfSetTo($id); \n";
+				
+				if ($id == $this->currentPageID()) FormResponse::add('CurrentPage.isDeleted = 1;');
 			}
 		}
 		FormResponse::add($script);
@@ -1038,6 +1045,52 @@ JS;
 	public function isCurrentPage(DataObject $page) {
 		return $page->ID == Session::get("{$this->class}.currentPage");
 	}
+	
+	/**
+	 * Get the staus of a certain page and version.
+	 *
+	 * This function is used for concurrent editing, and providing alerts
+	 * when multiple users are editing a single page. It echoes a json
+	 * encoded string to the UA.
+	 */
+	public function pageStatus() {
+		// If no ID is set, we're merely keeping the session alive
+		if (!isset($_REQUEST['ID'])) return 1;
+		
+		$page = $this->getRecord($_REQUEST['ID']);
+		if (!$page) {
+			// Page has not been found
+			$return = array('status' => 'not_found');
+		} elseif ($page->getIsDeletedFromStage()) {
+			// Page has been deleted from stage
+			$return = array('status' => 'deleted');
+		} else {
+			// Mark me as editing if I'm not already
+			$page->UsersCurrentlyEditing()->add(Member::currentUser());
+			DB::query("UPDATE SiteTree_UsersCurrentlyEditing SET LastPing = '".date('Y-m-d H:i:s')."'
+				WHERE MemberID = ".Member::currentUserID()." AND SiteTreeID = {$page->ID}");
+			
+			// Page exists, who else is editing it?
+			$names = array();
+			foreach($page->UsersCurrentlyEditing() as $user) {
+				if ($user->ID == Member::currentUserId()) continue;
+				$names[] = trim($user->FirstName . ' ' . $user->Surname);
+			}
+			$return = array('status' => 'editing', 'names' => $names);
+			
+			// Has it been published since the CMS first loaded it?
+			$usersCurrentVersion = isset($_REQUEST['Version']) ? $_REQUEST['Version'] : $page->Version;
+			if ($usersCurrentVersion < $page->Version) {
+				$return = array('status' => 'not_current_version');
+			}
+		}
+		
+		// Delete pings older than 3 minutes from the cache...
+		DB::query("DELETE FROM SiteTree_UsersCurrentlyEditing WHERE LastPing < '".date('Y-m-d H:i:s', time()-self::$edit_timeout)."'");
+		
+		echo Convert::array2json($return);
+		return;
+	}
 
 	/**
 	 * Return the CMS's HTML-editor toolbar
diff --git a/javascript/LeftAndMain.js b/javascript/LeftAndMain.js
index 76402928..dba239e7 100644
--- a/javascript/LeftAndMain.js
+++ b/javascript/LeftAndMain.js
@@ -1,4 +1,5 @@
 var _AJAX_LOADING = false;
+var pagePingInterval = 15;
 
 // Resize the tabs once the document is properly loaded
 // @todo most of this file needs to be tidied up using jQuery
@@ -865,9 +866,66 @@ function hideIndicator(id) {
 	Effect.Fade(id, {duration: 0.3});
 }
 
+var CurrentPage = {
+           id: function() { return $('Form_EditForm_ID').value; },
+      version: function() { return $('Form_EditForm_Version').value; },
+    isDeleted: function() { return $('SiteTree_Alert').getAttribute('deletedfromstage'); }
+}
+
 setInterval(function() {
-    new Ajax.Request("Security/ping");
-}, 5*60*1000);
+	if ($('Form_EditForm_ID')) {
+    	new Ajax.Request("admin/pageStatus?ID="+CurrentPage.id()+'&Version='+CurrentPage.version(), {
+			onSuccess: function(t) {
+				var data = eval('('+t.responseText+')');
+				var hasAlert = false;
+				
+				switch(data.status) {
+					case 'editing':
+						$('SiteTree_Alert').style.border = '2px solid #B5D4FE';
+						$('SiteTree_Alert').style.backgroundColor = '#F8FAFC';
+						if (data.names.length) {
+							hasAlert = true;
+							$('SiteTree_Alert').innerHTML = "This page is also being edited by: "+data.names.join(', ');
+						}
+						break;
+					case 'deleted':
+						// handle deletion by another user (but not us, or if we're already looking at a deleted version)
+						if (CurrentPage.isDeleted() == 0) {
+							$('SiteTree_Alert').style.border = '2px solid #ffd324';
+							$('SiteTree_Alert').style.backgroundColor = '#fff6bf';
+							$('SiteTree_Alert').innerHTML = "This page has been deleted since you opened it.";
+							hasAlert = true;
+						}
+						break;
+					case 'not_current_version':
+						// handle another user publishing
+						$('SiteTree_Alert').style.border = '2px solid #FFD324';
+						$('SiteTree_Alert').style.backgroundColor = '#fff6bf';
+						$('SiteTree_Alert').innerHTML = "This page has been saved since you opened it. You may want to reload it, or risk overwriting changes.";
+						hasAlert = true;
+						break;
+					case 'not_found':
+						break;
+				}
+				
+				if (hasAlert) {
+					$('SiteTree_Alert').style.padding = '5px';
+					$('SiteTree_Alert').style.marginBottom = '5px';
+					$('SiteTree_Alert').style.display = 'block';
+				} else {
+					$('SiteTree_Alert').innerHTML = '';
+					$('SiteTree_Alert').style.padding = '0px';
+					$('SiteTree_Alert').style.marginBottom = '0px';
+					if ($('SiteTree_Alert').style.display != 'none') $('SiteTree_Alert').style.display = 'none';
+				}
+			}
+		});
+	} else {
+		// We're not looking at a page, so at this stage, we're just
+		// pinging to keep the session alive.
+		new Ajax.Request("admin/pageStatus");
+	}
+}, pagePingInterval*1000);
 
 /**
  * Find and enable TinyMCE on all htmleditor fields