Most of the British left, broadly conceived, supported UK membership of the European Union (EU). During the 2016 referendum, a significant majority of Labour MPs, as well as their Green, Liberal Democrat, Scottish Nationalist and Plaid Cymru counterparts, campaigned for the “Remain” position. Polls suggested that this was generally in line with the aspirations of much of their voting base, especially younger, university-educated professionals concentrated in the major cities. The 2019 general election subsequently marked a turning point, especially in Labour's approach to Europe. In its worst election result since 1935 (in terms of seats) the party lost many traditionally solid “red wall” constituencies in England's post-industrial north, the West Midlands, and Wales, where majorities had, by and large, voted for “Leave” in the plebiscite. Many on the left questioned whether continuing implicitly to support Remain, explicitly advocating a “second referendum” position or even simply favouring a “soft” Brexit that kept the UK inside the European single market was an electorally sustainable position. It appeared to be so in the ongoing tumult of the immediate post-referendum period, when, on either side of the indecisive 2017 election, different “Brexits” could be envisaged and parliament was deadlocked. Nevertheless, traumatized by the referendum, its aftermath and then the 2019 election, Labour, along with much of the wider left, fell largely silent on the Europe question as the country “exited” and politics became consumed by the Covid-19 pandemic. Calls for rejoining the EU, or even strengthening ties, had become, at least among prominent left politicians, few and far between.

Prime Minister Boris Johnson's government, meanwhile, used its landslide 2019 victory to rapidly reorder the British economy and its relations with Europe. Having been elected on a promise to “get Brexit done”, Johnson concentrated power in the executive and deployed it assertively, and dysfunctionally, to take the UK out of the EU on 31 January 2020. In a narrow sense, Brexit was indeed “done”.