Recent declassified records show that the British Security Service, known as MI5, not only operated in the colonial territories but also in independent foreign territories in the Middle East. This article will show for the first time the activities in these territories of Security Intelligence Middle East (SIME), the regional headquarters of MI5, after the Second World War until its closure in 1958. By examining declassified records, this article will demonstrate that the regional role of MI5 was not to defend British interests against nationalist movements, but was instead quite narrowly focused on Communist movements in the region. It will further argue that the intelligence-collection activities and security measures implemented in these territories were largely limited by the general hostility towards Britain's military presence in the Middle East in the post-war period. This article will also explore the nature of the intelligence liaison between the representatives of MI5 and their Middle Eastern counterparts as well as with the British Secret Intelligence Services (SIS), known as MI6.