It is often said of chess — by those who don't play it — that it is socially useless. It is a solitary pursuit, anti-social even, and who ever heard of anyone's life being saved by chess? Yet 70 years ago, with the outbreak of the Second World War, the British Government found chess players to be uniquely useful in work which saved the lives of countless soldiers in the field: cracking the code — the Enigma — which the German Army used.

Three leading British chess players, Stuart Milner-Barry, Harry Golombek and Hugh Alexander, were assigned to Bletchley Park to join the mysterious organisation then known as the Government Code and Cypher School. Alexander — an Anglo-Irishman whose full name was Conel Hugh O'Donel Alexander — was eventually put in charge of the vital Hut 8, which was concerned with the breaking of the Naval Enigma, therefore playing an invaluable role in the Battle of the Atlantic.

It is not just because of the war's anniversary that I want to single out CHO'D Alexander: he was born 100 years ago and deserves much more than the obscurity into which his name has fallen. This is no doubt in part due to the secrecy of the professional work he undertook: I have in front of me a memoir of him by Sir Stuart Milner-Barry (who became a very senior civil servant), which bears the legend "Handle via Comint Channels Only" and underneath "Approved for Release by NSA [National Security Agency] 9-18-2007."

The memoir makes clear that Alexander was not as other men, or even other code-breakers: "We worked [at Hut 8] through the War on a continuous three shift basis. The night shift was not generally popular because everybody quickly became tired through lack of proper sleep in the day; but Hugh had a strange passion for working at night and used to put himself on nights for weeks on end. This did not prevent him working much of the day as well — he seemed to thrive on this strange regime."

Alexander was entirely consumed by the mind-boggling intellectual struggle. After the war, following a brief stint on civvy street, he returned to become the head of cryptanalysis at GCHQ, where he remained until his retirement in 1971, regularly refusing all promotions. On his retirement, he was offered a similar job at the NSA by the Americans, but he was already a sick man, dying in 1974 at the age of 64.