We've already seen the power of signals intelligence. Churchill loves being fed information from MI6's Ultra. Now it brings a vengeance for his American allies. They manage to bag the scourge of Pearl Harbor, C-in-C of the Imperial Japanese Navy, Admiral Isoroku Yamamoto.

Glyndwr Michael, the dead secret agent, has deposited his deceptive letters in Spain. Now the next phase of Operation Mincemeat begins. If Charles Cholmondely of MI5 and Ewen Montagu of Naval Intelligence have done their job right, the letters should make their way into Hitler's hands.