While Alan Turing and Gordon Welchman occupy the spotlight of Enigma codebreaking history, the vast majority of the day-to-day cryptanalytic work at Bletchley Park was performed by young women — linguists, mathematicians, crossword champions, and secretaries who had no idea what they would be asked to do when they received their mysterious letters from the War Office.
Mavis Batey, then Mavis Lever, was just 19 when she joined Bletchley Park in 1940. Assigned to the Italian naval section under Dilly Knox, she had no formal training in cryptography. Within months she had identified weaknesses in the Italian Navy's cipher system, and on March 25, 1941, she broke a message that revealed the Italian fleet's position before the Battle of Cape Matapan — a British naval victory that destroyed three Italian cruisers and two destroyers with over 2,000 Italian sailors lost. Admiral Cunningham later credited Ultra intelligence as decisive.
Later, in December 1941, Batey broke the German Abwehr Enigma traffic — a different variant than the one Turing worked on — which led directly to the identification of German agents operating in Turkey, including the notorious Eppler spy ring in Cairo. Her work was instrumental in ensuring Operation Bertram, the deception plan before El Alamein, successfully misled Rommel. She became the first woman to break an Abwehr cipher and later assisted in the Double-Cross system that turned German spies into British double agents.
Joan Clarke was recruited after solving a Daily Telegraph crossword puzzle in under five minutes — one of the methods used to recruit cryptanalysts. She became one of the few women to work directly in the Hut 8 team with Turing and was the highest-ranking female cryptanalyst at Bletchley Park, yet she was paid at a clerical grade rather than an analytical grade because of her sex. Churchill's intervention was required to rectify her pay.
At its peak, Bletchley Park employed approximately 9,000 people, of them roughly 6,500 were women. Most still do not have their stories told.