In the grand narrative of global climate governance, the evolution of national roles often reflects the broader transformations in the international political economy and the shifting priorities of domestic governance. The United Kingdom—birthplace of the Industrial Revolution and one of the archetypal advanced economies—presents a paradigmatic case of policy transformation in climate governance. Over the past three decades, Britain has journeyed from reluctant participant to active global leader, crafting a model trajectory from resistance to reform to leadership. This chapter investigates the evolution of the United Kingdom’s climate policy and governance framework, tracing its metamorphosis from a “troublesome member” within the European Community/European Union to an assertive and globally ambitious climate leader. It further assesses the continuity and innovations of British climate strategy in the post-Brexit era.