I can remember two students getting a severe rep for looping one which put a few wrinkles in the wings!Perhaps the ex QFI can remember this,about 1966 I think?
Your memory is good, although it might have been '67. I could put names to the perpetrators but shall desist for the time being
They started out with the aim of barrel rolling the old dear and had they persisted all would probably have been well. Unfortunately they changed their mind about half way around and attempted to pull through, that was what caused the problems! It was a tough old aeroplane though.
YS