The UK decision to leave the European Union (EU) has raised the question of what form the post-Brexit UK-EU relationship will take. This chapter explores the development of the UK government’s position since the June 2016 referendum through to the end of 2018 and the conclusion of a Withdrawal Agreement and the adoption of a Political Declaration on the framework for future UK-EU relations. In doing so, it highlights the persistent lack of domestic UK consensus on post-Brexit relations with the EU and the significant challenges the UK government has faced in reconciling the ambition of securing a new strategic partnership and a wide-reaching, bold and ambitious free trade agreement with its own red lines on leaving the customs union, the single market and the jurisdiction of the Court of Justice of the EU. The chapter explores, too, the EU’s response. A central concern is the extent to which that response is being shaped or determined by established principles underpinning the EU’s external relations. Regular references to the EU not being open to UK ‘cherry-picking’ and accusations more generally that the UK is seeking to ‘have its cake and eating it’ suggest those principles and the precedents set by the EU’s existing privileged partnerships are having a demonstrable impact on the EU’s position.