The code name for Bletchley Park, near Cambridge, the Second World War intelligence and cryptanalysis base. The name was not deliberately mysterious or secretive, it was, quite simply, the tenth of the MI6 codenamed bases.

Originally, it had been the home of Herbert Samuel Leon, a rich City finacier. He'd bought 300 acres of land in Buckinghamshire and developed sixty or so of them into his country estate. The house itself is a strange mixture of architectural styles, and is rather jumbled in design. When the Leons died, the Park was bought by a property developer called Captain Hubert Faulkner, who intended to flatten the buildings and sell the land for housing.

But the government intervened. Bletchley Park is some fifty miles northwest of London, and, at the time, was at a key intersection of roads, railway lines, and teleprinter services. In 1938, the Government Code and Cypher School, which was based in London, needed to move to a safer space to continue its intelligence work. Bletchley Park was in an ideal location, and so Station X was born and placed under the command of Alastair Denniston.

The first team of codebreakers, mostly academics, arrived at Station X in the summer of 1939, under the guise of Captain Ridley's Shooting Party.

Initially, the whole operation ran from within the nineteenth century mansion, with desks and teleprinters crowding every room, and corridor of the main house and the stables. But, as the numbers grew and grew, extra space had to be found. In October 1939 the first of the famous wooden huts were built to house the overspill. By 1941 it was necessary to add brick buildings to hold the overflow from those.

It was in Huts 3,6,4 and 8 that the Enigma decryption teams worked. They were only ever known by their numbers, for security reasons. Descriptive names could have leaked out far too easily. The huts worked in pairs. In Hut 6 were the teams of codebreakers focused on the Army and Air Force cyphers. They were supported by Hut 3 who converted the decyphered messages into intelligence reports. The German Navy messages were worked on in Hut 8, with Hut 4 handling the intelligence work. (The raw material came from the Y stations across Britain and abroad, who listened into enemy radio messages, and send the intercepts to Bletchley to be decoded and analysed.

Nobody was billeted in the Park itself. All the Station X workers lodged with local families, in pubs and in hotels in every village for twenty miles. They worked around the clock in three shifts, with buses shuttling them back and forth between their lodgings, though many travelled by bicycle. Alan Turing was renowned for cycling in his gas mask, not for fear of chemical attacks, but because he suffered terribly from hayfever.

As many as 12,000 people were stationed at Bletchley, but by March 1946 all of them were gone. When they left, the took away, or destroyed every last trace of their codebreaking exploits. It's almost unthinkable that the secrecy was preserved, all through the Second World War, and for so long after. But the place remained shrouded in mystery. Even after the bulk of the story had come out, and been turned into documentaries, and trashy novels, many of the Station X workers stuck with their customary silence.

It was only after they died that I discovered that my Great Uncle and Aunt had both worked there for years. And the old lady in the hospital bed next to me, a couple of years ago, had been there too. She wouldn't tell me what she did, despite my intense curiosity, although she was terribly amused by how the vacuum tubes that kept being found in the ground had confused people for so many years. She always then managed to steer the conversation back to the importance of organic gardening.

Winston Churchill described the immense secrecy of the success of the cryptanalysisas "the geese that laid the golden eggs and never cackled".