Mavis Batey

Codebreaker at Bletchley Park who broke the Italian naval Enigma before the Battle of Cape Matapan and the Abwehr Enigma on which the Normandy deception depended. Born on 5 May 1921 in Dulwich. She was reading German at University College London when the war interrupted her studies. In 1940, aged nineteen, she was sent to Bletchley Park and joined Dilly Knox's section. In March 1941 she broke into the Italian naval Enigma. The intercept began "Today is the 25th of March 1941, the day minus three", and she understood that an operation was being prepared. The traffic that followed allowed the Royal Navy to meet the Italian fleet off Cape Matapan and inflict a heavy defeat — its greatest victory in the Mediterranean. In December 1941, with Dilly Knox and Margaret Rock, she broke the Enigma of the Abwehr, German military intelligence. The consequence is hard to overstate: reading Abwehr traffic let the British see whether the enemy believed their deceptions. The Double-Cross system and Operation Fortitude — convincing the German command that the landings would come at the Pas de Calais — rested on that. Without a way to check that the deception was working, no such plan could have been risked. After the war she became a garden historian and a leading figure in the conservation of historic landscapes in Britain; her MBE was for that work, not for Bletchley, which she was not allowed to discuss. She died on 12 November 2013.