This book presents a comparative study of the historical experiences of Britons who entered the international civil service between 1945 and 1970 with those who worked and volunteered in international non-governmental and civil society organizations. International service assumed two forms after the Second World War. One was the international civil service, much of which was concentrated in the United Nations (UN) family of international organizations. The other was international civil society, comprised of older voluntary organizations that expanded their activities after the war, and new transnational civil society organizations created between the 1940s and the 1970s. The book assesses the respective influence of Britons in these sectors on the post-1945 development of international public policy and on Britain’s transition from a great power to one that sought to position itself as a leading contributor to international governance and voluntary activism. It presents a comparative analysis of the personal histories of hundreds of Britons who represented Britain at the UN and worked in the UN Secretariat; served in UN humanitarian, development, and social governance institutions and missions; participated in the world government movement; volunteered in the Friends Postwar International Service; and lobbied for decolonization and anti-racism through the Movement for Colonial Freedom.