My dissertation is a genealogy of thinking about the end of capitalism. I focus on twentieth century Britain – once Marx's locus classicus of capitalist production, and a destination for migrant radicals from around the world – and I use archives in five countries to explore how capitalism's changing spatial organization in the twentieth century transformed and undermined widespread expectations of capitalism's demise. I begin in 1918 with Britain at the core of global capitalism, and trace how Britain's increasing marginality to that world system after the end of Empire generated an intellectual crisis for aspirations to end capitalism. My research will bring together a group of influential economists, political theorists and politicians over two generations, including liberals, socialists, feminists and anti-colonial revolutionaries. It will place their thought in a transnational context, exploring how developments from afar drove political thought in Britain more than has been appreciated. By showing how visions of ending capitalism were once common, and by reconstructing changes in those visions over time as responses to changes in the structure of global capitalism, my dissertation will make significant contributions to both intellectual history and the emerging field of the history of capitalism. It will reimagine the rise of ideas of "the economy" and the post-imperial nation-state as well as capitalism's postwar stabilization and 1970s revolutions within capitalism by showing how these developments all unfolded in conversation with changing models for transcending capitalism. My dissertation is the first conceptual history of "transition", the attempt to outline various proposed routes out of capitalism. A work of political theory as well as history, it will excavate a rich, multivalent political concept. It comes amid a climate crisis and a revived socialist Left, when transitions are back on the agenda, and it hopes to contribute to rethinking the concept.