ABSTRACT
Despite a thick London fog which delayed the arrival of many of the attending dignitaries, the London Naval Conference opened with great glitter and ceremony in the Royal Gallery of the House of Lords, on 21 January 1930, with a speech of welcome from King George V. Attended by the world’s five major naval power – Britain, the United States, Japan, France and Italy – it would meet continuously until late April in an attempt to extend the regime of naval limitation that had been agreed to eight years earlier at a conference in Washington. But there was more to these naval disarmament negotiations than met the eye. Conferences of this sort provided manifest opportunities for the intelligence services of the host nation, as control over the telegraphic facilities into and out of the country allowed for the easy interception of communications made by the delegations of visiting powers. It was an advantage which the Americans had seized at the Washington Naval Conference of 1921-22 to read the Japanese diplomatic traffic, giving them a significant advantage in negotiations 1 At the London conference, one of the chief weapons in the British negotiating armoury was its similar ability to read most of the messages exchanged between the various delegations and their respective home governments. The British signals intelligence body, known as the Government Code and Cypher School (GCCS), ‘was one of the world’s largest code-breaking agencies [and] . . . possibly the best on earth between 1919 and 1935’.2 In the course of each month during 1929-31, for example, it developed a file averaging about 300 decrypted diplomatic intercepts, ranging over American, Japanese, Italian, French, Greek, Persian, Spanish, Scandinavian and other minor states’ transmissions.3
