At the end of the twentieth century, the United Kingdom's withdrawal from the European Union was a fringe idea, even on the political right, and the name “Brexit” had not been invented. Yet by the 2020s, it was the new reality of British economics, society and politics, both domestic and internationally. This dramatic change is the result of the referendum of 23 June 2016, in which 51.9 per cent, out of the 72.2 per cent of the electorate who voted, supported leaving the EU. Although legally the vote was only advisory – and arguably a supermajority should have been required for such a fundamental constitutional change – this narrow result quickly had a decisive, structural character. Half a decade afterwards, therefore, important connections between Britain and continental Europe which had expanded over more than half a century were contracting. In particular, flows of people between the two which had grown throughout this period were being reversed to a significant degree. Brexit also led to a wide-ranging upheaval in the UK. The country's politics were transformed in the three and a half years after the referendum, with deep new conflicts and electoral realignments, leading in the general election of 12 December 2019 to a substantial majority in parliament for the Conservatives, who had changed from a largely Eurosceptic party which nevertheless favoured EU membership into a party which was fundamentally hostile to European integration, which we can describe as Europhobic (following the approach of Kopecky & Mudde 2002). This election led in turn to the implementation of a “hard” Brexit, which excluded the UK from the European Economic Area (EEA, or the “single market”) as well as the EU itself, ending freedom of movement between Britain and the EU. Moreover, these changes did not stop with the UK's formal exits from the EU on 31 January 2020 and the single market on 31 December 2020. Brexit also radicalized the national conflicts in Scotland and Northern Ireland, threatening the very coherence of the UK state. The new administration (which itself emphasized its differences from its Conservative-led predecessors) operated in an authoritarian nationalist mode, and was widely seen as a hard-edged and ambitious (if somewhat inchoate) power formation, unusually prepared to dispense, so far as the balance of forces allowed it to, with certain democratic and international conventions.