Obituary: Keith Batey, Mathematician and Bletchley code-breaker

HE WAS one of the finest brains working on the German Enigma machine ciphers at Bletchley Park during the Second World War. Keith Batey was a pure mathematician and one of the code-breakers who carried out vital work in Hut 6, the section which broke the German army and air force Enigma messages.

He later moved to the specialist section that broke the Enigma messages of the Abwehr, the German military intelligence service. Batey's work unquestionably helped the Allies' cause and it was many years before those at Bletchley Park received their just recognition as they were all sworn to secrecy. It is often said that the boffins in Bletchley Park knew of Hitler's orders before his generals.

In more recent years Batey and his wife, Mavis, who he met at Bletchley, were involved in an advisory capacity in the making of the film Enigma and showed the Prince of Wales round Bletchley Park two years ago.

John Keith Batey was born at Longmoor, Cumberland. His father had been severely wounded on the Somme and his mother had to support the family on her wages as a part-time teacher.

Batey attended Carlisle Grammar School and then won a scholarship to read mathematics at Trinity College, Cambridge.

Another scholar at Trinity, Gordon Welchman, had started work at Bletchley Park on the outbreak of war and was head of a mathematical division. In June 1940, he assembled a group at Bletchley and Batey was one of his first recruits.

Batey, however, hankered after more active service and wanted to join the RAF. That was firmly squashed by senior officials and instead Batey went to Canada in 1943 with the Fleet Air Arm.

In fact his advance training was terminated as he had got married to a young girl at Bletchley called Mavis Lever. She worked in the German translation department and their talents led them to being separately recruited for top secret work with MI6. Their work at Bletchley brought them together and they were married in 1942.

Batey was ordered to return from Canada after only a few weeks of his advanced training as he was needed in a new section working on the Abwehr Enigma. Batey was to have a considerable personal impact into the deciphering during the remaining three years of the war.

In August 1943, he solved the Enigma ciphers of the Nazi party's own intelligence service. Three months later Batey cracked the cipher used by the Spanish military attachs in Berlin and Rome to report back to Madrid - then a hotbed of intrigue - on German and Italian military plans.

Batey was responsible for important breakthroughs in decrypting the Abwehr Enigma system thus helping MI5 to control the double agents and the German espionage network in Britain.Such intelligence was crucial to the Double Cross system - using German agents to feed misinformation back to Berlin. Of huge strategic importance it allowed the Allies to ascertain just what information the Germans did and did not know about the D-Day invasion plans.

The false leads about the proposed D-Day landings in the Pas de Calais required the double agents to inform Berlin that forces were being amassed in Suffolk. Through Batey's codes, the agents fed information that ensured Hitler maintained huge forces in the north.

After the war Batey joined the Foreign Office, served in the high commissioner's office in Ottawa and then with the Civil Service in London before joining, in 1955, the Royal Aircraft Establishment at Farnborough.

In 1967 he was appointed the financial officer at Oxford University and in 1972 treasurer of Christ Church College. When he retired in 1985, Batey contributed to the official history of Bletchley Park which has still not been released by GCHQ in Cheltenham. He also wrote chapters in a forthcoming history of Trinity College, Cambridge entitled Portrait of Trinity.

The Bateys never talked of their work at Bletchley, but in recent years they have been able to gain some much deserved recognition. In the film 2001 Enigma, both Keith and Mavis were on hand to act as consultants and they are credited at the end of the film. They provided personal insight to the film's stars, Kate Winslet and Dougray Scott.

In July 2008, the Bateys were on hand when Prince Charles and the Duchess of Cornwall visited Bletchley Park.

In a reconstruction of Alan Turing's office they met the Bateys who gave a delightful presentation about working there. Keith caused some amusement when he apologised for "jiggering" or, as he had to admit, breaking, the Abwehr Enigma machine on which they had planned demonstrations.

Keith Batey is survived by his wife and by a son and two daughters.