One of the great Bletchley codebreakers, Mavis Batey's work to decipher Germany’s Enigma messages was crucial to the success of D-Day.

When I arrived, he said: "Oh, hello, we’re breaking machines, have you got a pencil?" That was it.

Mavis Batey recalls meeting Dilly Knox. From Mavis Batey's obituary, The Telegraph (2013)

Mavis Batey (1921 – 2013) was one of the Bletchley break-in experts: World War II codebreakers who infiltrated German codes and ciphers, previously believed to be unbreakable. Mavis contributed significantly to the important field of Cryptography, using mathematical techniques to crack wartime ciphers and protect sensitive information.  

Born Mavis Lilian Lever in Dulwich, London, she was studying German at UCL when the Second World War broke out. Mavis interrupted her study to contribute to the war effort, volunteering as a nurse. A talented linguist, Mavis was offered a place at the Government’s Code & Cypher School, after deducing that Morse Code place name S-T-G-O-C-H was not “St Goch”, but Santiago, Chile. At just 19, Mavis was working on the Enigma research team at Bletchley Park in a largely female unit, run by veteran cryptographer Dilly Knox.  

Working the entirety of the war, Mavis is best remembered for an early break in, deducing a character in the Italian Enigma system and, later, decoding a message which read: “Today’s the day minus three”. The team took almost the whole 3 days to decode a string of messages until it was revealed: the Italians were planning to ambush a critical supply convoy. The allies intercepted this and secured a Navy victory at the Battle of Cape Matapan. 

Mavis went on to crack the German Abwehr Enigma code, which verified that Allied intelligence had successfully fooled Hitler into believing that their main invasion would occur at Pas-de-Calais rather than Normandy. This was key to the success of the D-Day landings. 

Mavis married fellow Bletchley codebreaker Keith Batey and settled in Surrey, where she developed an interest in landscape history and became a dedicated campaigner for preserving national sites from redevelopment. Mavis’ efforts led to the 1974 Town and Country Amenities Act, the first legislation to recognise historic gardens alongside listed buildings. 

From codebreaker to conservationist, Mavis Batey never failed to speak her mind: 

You should make your voice known. You never know how things are going to turn out.

Top photograph: Courtesy of the Batey family.

Sources and explore further