There are now enough books about Bletchley Park for it to become part of national mythology, along with the Tudors, Trafalgar, Waterloo, the Somme and Winston Churchill. Rather than rehearse the Enigma story, however, Sinclair McKay describes what happened to the organisation that became GCHQ (Government Communications Headquarters) during the immediate postwar years. This was the crucial period when intelligence effort was redirected from fighting a hot war against Germany and Japan to beginning a Cold War against the Soviet Union. It is a neglected period in popular history and McKay does well to bring it to life.
When the second world war ended, what we now know as GCHQ was part of MI6, under whose wing it had been since the early 1920s. But such was the success of signals intelligence during the war that the cuckoo outgrew the nest and became a sister organisation, answerable, like MI6, to the Foreign Office.
This transition involved relocation from Bletchley to Eastcote, a sprawl of military huts on the northern edge of London, and then more happily to Cheltenham, where it remains. It also entailed the reorientation of the organisation’s worldwide intercept effort and cipher attack, so that its focus was on monitoring and containing any effort by the Soviet Union to expand its power and influence. That was never GCHQ’s sole target — a fact acknowledged, if not much emphasised, here — but it was the big one.
Wisely, McKay draws on the scholarly work of Richard Aldrich in his sketch of this process, emphasising three or four main themes. The first is the importance of the Y Service, a worldwide network of monitoring stations that picked up the signals that were sent to GCHQ for analysis and decryption — Bletchley’s raw material.