Where has my diff view gone?

[Noel]

There used to be a diff view to the right. It was there yesterday. Today it's gone??????????

How do I roll back to v 4.2.7 before this feature was removed???
(And why would you remove the most useful feature in the app!!???????????) 

Aah.. never mind. Somehow it was minimised. I managed to grab it by the handle and slide it open. Frikken demoralising though.