The daughter of Barnes Wallis, the scientist behind the "bouncing bomb" used to such devastating effect on the Dambusters raid, has spoken of the "absolutely marvellous" bravery of the airmen involved as well as her father's "profound" upset at the mission's high casualty rate.
Mary Stopes-Roe, 85, made the remarks ahead of a series of events marking yesterday's 70th anniversary of the daring attack.
In order to have a chance of destroying the dams in Nazi Germany , the bombs created by her father had to be dropped with great precision, meaning some of the crews had to make repeated runs over the heavily defended targets, at low altitude.
Praising the perseverance of the airmen, Stopes-Roe said: "I think that's simply the training of good airmen.
"You have your instructions and you carry them out.
"The skill of some of those flights, amazing, not many could have done it.
The bravery; absolutely marvellous."
Of the 133 aircrew who took part, 53 were killed. Stopes-Roe, who married the son of Marie Stopes, the birth control pioneer, said the heavy losses had weighed on her father.
"The death rate after the dams raid upset him so profoundly for the rest of his life ... that's why he would never allow a test pilot to test fly the 'swing wing' [a revolutionary aircraft he developed later] as he said he would never endanger another man's life.
"If he was here today his thoughts would be with the crews."
She said he would be "amazed" at the commemorations planned for the 70th anniversary, which included a flypast of wartime aircraft at the Derbyshire reservoir where the original squadron trained, and a sunset ceremony at RAF Scampton at about the time the Lancasters took off from the Lincolnshire base on the mission.
"He did love his squadron, they were his boys. I love the old planes and he did too," Stopes-Roe said.
Dropped by the Lancasters flown by 617 Squadron, Wallis' bomb - officially codenamed Upkeep - breached the Eder and Mohne dams and damaged another, the Sorpe dam, on the night of May 16/17, 1943.
The dams served the Ruhr valley, Germany's industrial heartland, and the attack was credited with disrupting water and electricity supplies for the manufacture of war munitions.
While the impact on the war effort has since been debated, the effect of the audacious raid, and the revolutionary technology involved, on British morale has never been questioned.
In the interview posted on the RAF website, Stopes-Roe recalled how the idea for the bouncing bomb was, in part, inspired by marbles that she and her siblings played with as children, and how her father had conducted experiments in her mother's old washtub.
"My sister and I have a little dispute about this. They were certainly her marbles, but the idea of bouncing balls or whatever over water is well known. I remember during holidays he taught us how to do 'ducks and drakes' over water.
"He could spin nine to 11 hops over the water, my stones went plop. It's not an unknown feature of impact between hard things and water.
"The point was you had to get it near enough to the dam; it's got to get down to have enough explosive to blow it up as you're very unlikely to hit the dam from the top.
"In April 1942, he wanted to try the idea out for himself with something that was round: a marble.
"He had a catapult made and he borrowed my mother's old washtub and it was simply and purely experimental to see if a round ball as opposed to a flat stone would bounce successfully over water.
"I remember my father doing it, we were all there. What he was looking at was not, would it bounce, but what angle would it best bounce at. The angle was very important, as became evident in the final outcome. It had to be from a certain height above the water and certain distance from the target.
"The experiment with the bathtub was the first effort of trying height, angle of propulsion and distance from the water.
"My brother, Barnes, remembered being told to see whether the marble bounced over or under a piece of string."
She said that initially her father had faced frustrations in trying to get his ideas accepted by the authorities.
"It was extremely difficult for him to convince the authorities of anything at all. It seems to me that he was one step ahead all the time. People stopped making his inventions, putting them into practice or it took them a long time; it must have been very frustrating for him."
Stopes-Roe said that Sir Arthur "Bomber" Harris had been particularly dismissive when presented with the idea for the bouncing bomb, saying, 'Oh nonsense, take it away.'
"My father resigned," she said. "Because he was so upset about all that. But they hoiked him back."
She recalled that the family were on holiday in Dorset at the outbreak of war: "We camped as a family every summer and at the moment when the loudspeakers went round on September 1 to tell the crowd that evacuations were going on from London and blackout regulations were coming into force, we were having tea in the square in Wimborne Minster.
"I remember my father jumping up and saying, 'I shall have to go home immediately and see to the blackout,' and off he went. I have the letters from my father to my mother explaining why she couldn't come home until he had fixed all the blackout and found out what was likely to happen about gas attacks and incendiary attacks."
Partly as a safety measure, the young Mary was packed off to boarding school in Salisbury. Her brothers, Barnes and Christopher, were already at boarding school in Wiltshire.
"I would write a letter every Sunday. Messages from home were nothing but good cheer. One thing from my generation was the courage of our parents and teachers; I was never made to feel afraid."
She added: "[My father] was always working. All through the 30s he had his study at the top of the house where he wasn't going to be disturbed. He worked very hard, but when he appeared he was great fun.
"In the war, being away, I didn't realise how hard he was working. Looking at his diaries now I think, 'My goodness, how did he do it?' He felt he needed to make a contribution and felt very strongly about defending ourselves.
"I always admired him. I think he was a great man. He tried to put into practice all that he believed and felt was the right thing to do. He was a lovely father, he was strict, no nonsense and your manners had to be decent but I didn't really know what he did. After the war, I suppose I thought wow, my dad did that.