This study seeks to trace federalists’ continuous effort to envision and plan for the end of the empire from 1884 to 1945. While British federalism changed a lot during this period, there was a constant concern with the post-imperial world order and this thesis studies the federalist texts based on the context of the contemporary reckoning with the shifts to the UK’s geopolitical standing. Seen in this way, the British federalists were not only important in developing political theory, but also one of the earliest and most serious examples of attempting to pre-empt and influence the dissolution of the British Empire. In order to do the tradition of British federalism justice, this thesis studies the central federalist organisations—Imperial Federation League (1884–1893), The Round Table (1909–today) & Federal Union (1939–today)—as well as the activity and careers of their members. Some of the key figures are Lord Lothian, Lionel Curtis, Leo Amery, W. T. Stead, F. A. Hayek, Harold Laski, William Beveridge, Barbara Wootton, and Lord Rosebery. As such, the thesis applies a close con¬textual reading of the federalist texts as a framework for understanding contemporary geopolitics, entwined with British public life, rather than as a series of isolated constitutional schemes. I will argue that one can find an early British example of a discourse on post-imperial global order within the British federalist tradition. The federalists developed a number of narratives as to how and why the British Empire should end, principally informed by their relationship to history and the emplotment into which they inscribed themselves. This thesis surveys a transition from preservationist narratives—whose main aim was to preserve British cultural influence—to utilisationist narratives—aspiring to utilise British imperial institutions and the UK’s global standing in order to further the progress towards a global union. This text demonstrates how this aspect of federalist thinking is relevant to its contemporary political discourse, and how the fundamental elements of this transition were already in place following the First World War. It reframes the tradition of British federalism, not only as an important hub for the development of ‘the federalist idea’, but as a way of thinking about and discussing the post-imperial world order.