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 would work together, was an unprecedented act of intelligence co-operation, beginning what has become known as the Special Relationship.

It grew out of speeches by and private understandings between Churchill and Roosevelt. The actual exchange of ‘cryptographic information’ was initiated by Stewart Menzies, Chief of MI6 (Bletchley Park was acquired, set up and run by MI6 until it became GCHQ, an independent agency, in 1945). It wasn’t all gas and gingerbread, with reservations on both sides. Some British did not trust the Americans to keep their greatest secret and eventually Churchill had to rule that there should be ‘complete co-operation’, i.e. sharing the work, not just the results.

Equally, some Americans were Anglophobes, either because of their perceptions of Irish history (like the current US president), or because they didn’t want to do anything that might help preserve the British Empire, or simply because Bletchley’s achievements outmatched their own. Also, on the American side especially, inter-agency fiefdoms and personal rivalries sometimes hindered full co-operation. But they were swept away by the irresistible floodtide of Bletchley’s work: ‘British success in this field represents, without question, the most astounding and most important cryptanalytic and intelligence achievement in all history,’ America’s leading codebreaker declared.