On the 17th May 1943, 133 airmen set out in 19 Lancasters to destroy the Möhne, Eder and Sorpe dams. 56 of them did not return. Despite these catastrophic losses, the raid became a propaganda triumph. The survivors were feted as heroes and became celebrities of their time. John Nichol retraces the path of 617 Squadron's most dangerous sorties as their reputation called them into action again and again.