Over four decades as a diplomat, Sir Frank Roberts dealt with headline issues, including policy towards Germany during the years of appeasement, the Second World War alliance with the Soviet Union, the origins of the Cold War, NATO affairs, the Berlin and Cuban Missile Crises, European integration, and relations with the Federal Republic of Germany. Collaborating with the renowned American diplomat, George F. Kennan (the cryptonymous author ‘X’ of an influential 1947 article), his despatches from Moscow in 1946 shaped Britain’s Cold War strategy. In 1954 he played an integral part in the diplomacy behind the rearmament of the Federal Republic and her incorporation into NATO, helping to build an enduring structure of transatlantic security. Roberts’ career sheds new light on British foreign policy across an era in which Britain slipped from global pre-eminence to regional power status.