Behind the Five Eyes intelligence alliance

In February 1941 four US officers were landed from a British warship at Sheerness, bundled into vehicles and driven to Bletchley Park, Buckinghamshire, a large redbrick house amid wartime huts. They were greeted at midnight by the head of Bletchley with sherry, whisky being in short supply. They carried with them a secret device called the Purple Machine, which deciphered previously impregnable Japanese communications. In return, they were given full details of Bletchley’s breaking of the German Enigma cipher. Yet it would be another ten months before the US entered the war. This exchange between two governments of their greatest secrets, with no formal agreement beyond an understanding that they