The British Government had long been aware of the strategic importance of the dams in the Ruhr region of north west Germany, particularly in providing water and energy.
As early as 1937, the Air Ministry drew up a list of targets which included three of the largest: the Mohne, the Eder and the Sorpe — all massively reinforced with steel and concrete.
The Ministry recognised that if these key dams could be breached, then devastation of almost Biblical proportions could be inflicted on the Ruhr.
The problem was how. The narrowness of the target made a direct hit from the air almost impossible and even if it were, no conventional bomb dropped by the RAF would smash such immense structures.
Nor were standard naval torpedoes of any use, since each dam wall was protected on its reservoir side by heavy netting.
But one fertile mind was determined to solve the problem. He was English scientist and inventor Barnes Wallis, and his answer was a bouncing bomb.
As a senior designer at the Vickers aircraft company, Wallis had already displayed his gift for invention before the war through his work on the R100, at its launch the largest airship in the world, and the Wellington bomber, whose innovative airframe, made of a lattice structure of interconnected metal beams, proved magnificently robust in combat.
‘In my whole experience of aeronautical engineers and inventors, I have never come across one I consider more able,’ says Fred Winterbotham, the Air Ministry’s Director of Intelligence.
Born in 1887 in Derbyshire, Wallis was the son of a doctor who contracted polio in middle-age, leaving him permanently disabled and his family in straitened circumstances.