The US Embassy in London has long played a leading institutional role in the Anglo-American relationship, but few historians have examined that role. This article covers the early Cold War era of 1945-1953 — a formative period in the Anglo-American relationship — and considers issues such as the Embassy's organization, the range of work in which it participated and the contributions of the successive ambassadors. Prominent policy issues during this period included the European Recovery Plan and the Berlin Crisis. It is contended that the Embassy reached the peak of its peacetime importance under US Ambassador Lewis Douglas from 1947-1950, and that its most important role was in policy liaison. This liaison function stemmed from the need to coordinate British and US policies in the developing Cold War, and helped to lay the foundations for the long-term 'special relationship'. The article provides fresh insights into Anglo-American diplomatic bonds in a formative period.