Help Diffing a Content fragment

Hi All,

We had a workflow working where we sent a CF for review and the reviewer could diff the contents of the CF.

The UI that the reviewer sees isn't great but by doing this we used to get to see a diff:

1. selecting the item to review from their inbox
2. selecting payload 
3. selecting timeline on top left
4. clicking on versions
5. selecting the newest version
6. SELECTING THE COMPARE BUTTON

Oddly the compare button has disappeared. I can't find the hook that has removed this.

I should add that the workflow does the following:

Start -> lock payload -> content reviewers -> approve -> unlock -> publish

                                                                    -> reject -> unlock

Thanks in advance for any tips on getting the compare button back.