The Foreign Office ‘Thought Police’: Foreign Office Security, the Security Department and the ‘Missing Diplomats’, 1940 – 1952

ABSTRACT The protection of diplomats, embassies and sensitive information has always been an important aspect of diplomacy. Today, security is an accepted norm of day-to-day diplomatic work, yet the importance of security in the UK Foreign Office was not always appreciated, with the department witnessing embarrassing security lapses and scandals during the first half of the Twentieth Century. This article highlights the importance of security to diplomacy, offering the first significant study of the origins and early development of the Foreign Office’s Security Department, established in 1946. It also explores the tensions between security officials and the wider Foreign Office, which indicate the extent to which organisational and internal cultural issues stymied good diplomatic security, issues that were laid bare in the aftermath of the defection of Foreign Office officials Guy Burgess and Donald Maclean in 1951.