The European Union’s Common Commercial Policy (CCP) has shaped Europe and its relationships with the rest of the world for six decades by giving central EU institutions the ability to negotiate trade deals, defend against foreign trade practices, and set the trade policy agenda for the Union. The United Kingdom often plays a central role in EU trade politics: it has the second largest GDP of any member state, is the bloc’s largest exporter of services, and has long been a mainstay of the EU’s trade liberalization agenda. This chapter examines the role of the UK in setting current EU trade policy in order to draw conclusions about the likely effects of Brexit, using data from three case studies of recent trade agreements – the EU-Canada Comprehensive Economic and Trade Agreement, the Transatlantic Trade and Investment Partnership, and the EU-Singapore Free Trade Agreement – to analyze critical trade policy decisions and the coalitions supporting them. It concludes that the departure of the UK from the Common Market will have a strong destabilizing effect, not just on the economic and social wellbeing of European countries, but also on the often tenuous political consensus that underlies the CCP.