The UK-EU negotiations for new arrangements to cover trade in goods, following the UK’s decision to leave the EU, were long and complex. What lessons might politicians, trade negotiators, and academics learn from this long-drawn-out saga? This article focuses on five of the ways in which the UK misplayed, misunderstood, or misrepresented the consequences of Brexit. First, there was no plan for Brexit. Second, the implications for the Irish border and peace progress were not appreciated. Third, World Trade Organization (WTO) rules were not understood. Fourth, by threatening to break international law the UK undermined its credibility as a negotiating partner and increased the EU’s resolve to protect its market. Fifth, Boris Johnson’s unwillingness to acknowledge that leaving the EU’s customs union and Single Market would result in UK-EU trade barriers, distorted debate and raised unfulfilled expectations.