IIRC, the Syerston Vulcan was one of the Mk 1 prototypes which had been aerobatted frequently. The SBAC shows in the early 50's had both the Victor and the Vulcan doing improbable things for a 4 engined aircraft in front of the ministers in charge of the cheque books. You have to remeber it in context that it was considered only one aircraft would get the order.
Both the Victor and Vulcan prototypes crashed - metal fatigue?