Sir Stewart Menzies, the wartime chief of MI6, was wily, enigmatic, ruthless, clever and extremely posh. He was said to be the illegitimate son of Edward VII, a rumour that was probably untrue but which he refused to deny.

The grandson of a wealthy whisky baron, a gallant veteran of the First World War, he rode to hounds, never missed a day at Ascot, and drank, a lot, at White’s Club. But behind the military moustache and upper-class manner was a steely mind. Menzies led MI6, from 1939 to 1952, for the most part brilliantly, and effectively brought foreign intelligence into the modern age.

He supervised the code breaking at Bletchley Park, controlled the secret material obtained there with great skill, and attended more than