My late father, Professor AD Baxter, who was a propulsion researcher at the RAE, was present at a meeting to discuss how Barnes Wallis’ bouncing bomb could best be used to achieve the destruction of the dam, without pulling short or bouncing over the top.
At this point, Wing Commander Dann ambled into the conference and, on asking what was being discussed, picked up a wooden ruler, stuck a pin in both ends to represent the towers on either end of the dam.
He explained that, if the sequence of bounces of the bomb were known, then a simple sighting system, à la the ruler, could be constructed to ensure that the bomb struck the lower wall of the dam. And so it proved…
My father remained a good friend of Air Commodore Dann. As a young man, I was privileged to dine with them both on several occasions.
The Baron of Earlshall