D-Day, 6 June 1944, the turning point of the Second World War, was a victory of arms. But it was also a triumph for a different kind of operation: one of deceit, aimed at convincing the Nazis that Calais and Norway, not Normandy, were the targets of the 150,000-strong invasion force. The deception involved every branch of Allied wartime intelligence - the Bletchley Park code-breakers, MI5, MI6, SOE, Scientific Intelligence, the FBI and the French...