I've been away from this thread for a while.
Observations and questions on latest info:
2600ft at the top of a loop, if it is accurate, is way too low.
100kts at the top of a loop is way too slow; and I know stalling is dependent on AoA. The Hunter, in RAF service, did not have an AoA gauge. Did the naval T7/T8 which was used for Bucc checks? I don't really know. Had the civilian operator of this aircraft retro-fitted an AoA gauge? Does anyone know. AoA is crucial at that speed.
If he was at 100 kts at the top of the loop, with any aileron input the aircraft would have been exposed to an inverted spin from which there would have been no recovery.
AH has a total of 40 hours on the Hunter collected over 4 years. Well, I'm sorry, but IMHO that is nowhere near enough type experience for anyone to be doing this sort of flying. Years ago in the Service, no-one would have been cleared to do solo low-level aerobatic displays at air shows without first amassing several hundred hours on type, if not over a thousand.
Attention should perhaps focus on the system which cleared him to do it.