Vulcan VX770 was a hybrid; it was the original first prototype which had ultimately been fitted with Conway engines at Hucknall for engine development testing. It lacked the strength of the Mk1 and with lower structural weight and around 70000 lb of thrust compared to the original 26000 lb of thrust, it would have been a very 'hot ship' indeed. But the most serious issue is that RAF and company test pilots had routinely been flying wholly unnecessary aerobatics in the aircraft; it had often been rolled, and, on at least one occasion, it had actually been looped. A fact that had been covered up and probably wasn't made known to the crash investigators. Rolls-off-the-top had also been flown, so it is highly likely that the aircraft had been substantially damaged by other pilots before the Syerston crash.