This film follows the former bomb-aimer as he travels to France and Germany to rediscover his past and relive the raid on the Sorpe dam which, along with the Möhne and Eder dams and two minor ones, was attacked by a force of 19 low-flying Lancaster bombers on May 16, 1943.

The aim was to drown Germany’s industrial heartland, the Ruhr, by unleashing huge quantities of water into it.

However, although the Möhne and Eder dams were breached, the Sorpe held firm, the bouncing bomb released against it only crumbling the top section, much to Johnny’s lasting regret.

Now 86, and thought to be one of only two British Dambusters still alive, he sets off on a final mission to discover why the raid failed.

He also goes in search of his old Lancaster, one of 23 aircraft modified to carry a bouncing bomb, the brainchild of Barnes Wallis.