In the real Operation Source, Aitken was one of two divers in the four-man crew of midget submarine X-7, commanded by Lieutenant Godfrey Place, one of six midget submarines (or X-craft) which were towed across the Norwegian Sea to attack the battleship in its heavily protected anchorage at Altenfjord in September 1943.

Churchill called Operation Source a naval episode of highest importance: Place and Donald Cameron (the Scottish captain of X-6) were awarded the VC, while Sub-Lieutenants Richard Kendall and John Lorimer, and Aitken himself, were awarded DSOs.

The son of a Norwich doctor, Robert Aitken was born on January 1 1923 and educated at Oundle, after which he was articled as an accountant; but as soon as he was able he volunteered for the Navy as a seaman. He passed out of HMS King Alfred in 1942 top of his class, and volunteered for special duties . It was in a classroom at HMS Dolphin, Gosport, that Aitken and a group of officers and ratings were told that they had volunteered to be charioteers (crew of two-man “human torpedoes”). He enjoyed the training, later observing: “If you give a teenager what is essentially an underwater motorbike, that’s great fun. ”

Post-war, Aitken completed his articles and joined a firm in London. In 1951 he married Anne Hunt, and moved to R Hunt & Co, his wife’s family’s firm where he became managing director.