Index: lams_common/src/java/org/lamsfoundation/lams/learningdesign/RandomGrouper.java
===================================================================
diff -u -rb25a6d2d1cebe3c69d4af018aa14198533a0d4c5 -r5a04937692e2c67b3c27bb9ea181635038a6d09f
--- lams_common/src/java/org/lamsfoundation/lams/learningdesign/RandomGrouper.java	(.../RandomGrouper.java)	(revision b25a6d2d1cebe3c69d4af018aa14198533a0d4c5)
+++ lams_common/src/java/org/lamsfoundation/lams/learningdesign/RandomGrouper.java	(.../RandomGrouper.java)	(revision 5a04937692e2c67b3c27bb9ea181635038a6d09f)
@@ -103,12 +103,33 @@
     }
     
     /**
+     * Need to be able to force a user into a particular group for group based branching in preview. 
+     * So this is a non-random random. Bleah!
      * @throws GroupingException 
      * @see org.lamsfoundation.lams.learningdesign.Grouper#doGrouping(org.lamsfoundation.lams.learningdesign.Grouping,java.lang.Long, java.util.List)
      */
     public void doGrouping(Grouping randomGrouping,Long groupId, List learners) throws GroupingException
     {
-    	doGrouping(randomGrouping, (String)null, learners);
+    	if ( groupId != null ) {
+	    	Iterator iter = randomGrouping.getGroups().iterator();
+	    	Group selectedGroup = null;
+	    	while (iter.hasNext() && selectedGroup==null) {
+				Group group = (Group) iter.next();
+				if ( group.getGroupId().equals(groupId) ) {
+					selectedGroup = group;
+				}
+			}
+	    	if ( selectedGroup == null ) {
+	    		String error = "Tried to add users to group "+groupId+" but group cannot be found.";
+	    		log.error(error); 
+	    		throw new GroupingException(error);
+	    	}
+	    	selectedGroup.getUsers().addAll(learners);
+    	} else {
+    		// normal random !!!
+        	doGrouping(randomGrouping, (String)null, learners);
+    	}
+
     }
     
     //---------------------------------------------------------------------
Index: lams_common/src/java/org/lamsfoundation/lams/learningdesign/SequenceActivity.java
===================================================================
diff -u -r97612142f4697066beb66064e83ff31fef1712b9 -r5a04937692e2c67b3c27bb9ea181635038a6d09f
--- lams_common/src/java/org/lamsfoundation/lams/learningdesign/SequenceActivity.java	(.../SequenceActivity.java)	(revision 97612142f4697066beb66064e83ff31fef1712b9)
+++ lams_common/src/java/org/lamsfoundation/lams/learningdesign/SequenceActivity.java	(.../SequenceActivity.java)	(revision 5a04937692e2c67b3c27bb9ea181635038a6d09f)
@@ -186,7 +186,7 @@
 		this.branchEntries = branchEntries;
 	}
 
-	/** Get the groups related to this sequence activity, related via the BranchEntries */
+	/** Get the groups related to this sequence activity, related via the BranchEntries.  */
 	public SortedSet<Group> getGroupsForBranch() {
 		
 		Set<BranchActivityEntry> mappingEntries = getBranchEntries();
@@ -195,7 +195,12 @@
 		if ( mappingEntries != null ) {
 			Iterator mappingIter = mappingEntries.iterator();
 			if ( mappingIter.hasNext() )  {
-				sortedGroups.add(((BranchActivityEntry) mappingIter.next()).getGroup());
+				// Not all the BranchEntries have groups - when in preview, if the user selects a different
+				// branch to their expected branch then a group may not exist yet.
+				Group group = ((BranchActivityEntry) mappingIter.next()).getGroup();
+				if ( group != null ) {
+					sortedGroups.add(group);
+				}
 			}
 		}
 		
Index: lams_common/src/java/org/lamsfoundation/lams/lesson/service/LessonService.java
===================================================================
diff -u -rb25a6d2d1cebe3c69d4af018aa14198533a0d4c5 -r5a04937692e2c67b3c27bb9ea181635038a6d09f
--- lams_common/src/java/org/lamsfoundation/lams/lesson/service/LessonService.java	(.../LessonService.java)	(revision b25a6d2d1cebe3c69d4af018aa14198533a0d4c5)
+++ lams_common/src/java/org/lamsfoundation/lams/lesson/service/LessonService.java	(.../LessonService.java)	(revision 5a04937692e2c67b3c27bb9ea181635038a6d09f)
@@ -246,13 +246,14 @@
     
 	/**
      * Perform the grouping, setting the given list of learners as one group. Currently used for chosen grouping and 
-     * teacher chosen branching
+     * teacher chosen branching, and for group based branching in preview (when the user selects a branch that would 
+     * not be their normal branch).
      * @param grouping The grouping that needs to have the grouping performed.. (mandatory)
      * @param the id of the preferred group (optional)
      * @param learners to form one group (mandatory) 
      */
    public void performGrouping(Grouping grouping, Long groupId, List learners) throws LessonServiceException {
-		if ( grouping != null && grouping.isChosenGrouping() ) {
+		if ( grouping != null  ) {
 	       	Grouper grouper = grouping.getGrouper();
 	       	if ( grouper != null ) {
 	       		grouper.setCommonMessageService(messageService);