William, even if cracks had been discovered (and they may not, partly because of the different role and partly because it was a later design anyway), it wouldnt have been the end of the world. In 1976/77, cracks were discovered in the wings of Trident 3s and all had to be modified with reinforcment plates and new (old) wingtips. Similarly, in 1990, 2ft long cracks were found in the engine pylons of BA’s 767-300ERs, barely a year old, because the RB211-524 engines were a tonne heavier than the P&W or GE engines that had so far been sold with the aircraft. Neither of these incidents meant an end to the flying of these aircraft so if the V.1000 had gone ahead and if cracks had been found, I doubt it would have been the end of the world. The RAF retired the Valiant because it was the oldest and least technologically advanced of the V bombers and the Vulcan and Victor were in service and able to do the job better by 1964.