Spying and deception were two aspects of the Second World War in which the British consistently outwitted the opposition. The breaking of the Enigma code enabled the boffins of Bletchley Park to read German encrypted messages, as a result of which Churchill and his commanders could anticipate the enemy’s military manoeuvres; MI5’s XX or Double Cross Committee claimed to have detected every German spy in this country, turning many of them into double agents. The great master of practical deception was Lieutenant-Colonel Dudley Clarke, who honed his skills in the Middle East when Rommel’s Afrika Korps was threatening to overrun Egypt, and was later described by Field Marshal Alexander as having done more than any other individual to win the war for the Allies. Be that as it may, Clarke’s more conventional colleagues were shocked to learn that, with Rommel’s forces only a hundred miles from Cairo, he had been arrested in Madrid, dressed as a middle-aged woman.

Quite what Clarke was doing in Madrid was never made clear, but two years after his arrest he and his Spanish hosts were to play critical roles in what Hugh Trevor-Roper described as ‘the most spectacular single episode in the history of deception’. By the early summer of