Long before Brexit took shape, the UK's troubled relationship with the EU had left destructive and divisive marks on its internal politics. Deep-rooted and long-held anxieties about the EU's perceived assault on British sovereignty and identity had spawned Eurosceptic parties, had widened divisions within existing political parties and exerted increasing pressure for a referendum on the UK's membership of the EU. Countless column inches, extensive media coverage and hours of political debate about the merits and mistakes of the UK's relationship with the EU had punctuated British politics since its accession and long before the 2016 vote. In the days, months and years after the Brexit referendum, the volume of commentary and critique exploded. In one of the first and best-selling Brexit tomes, Tim Shipman (2016) recounted the extraordinary tale that is the Brexit referendum and its aftermath. It stands as a rigorous and engaging account of that early Brexit period. However, for all its detail, depth and rigour, it is an incomplete and skewed study of the Brexit story because there is little to no consideration of the “Irish question” – the singular issue that would come to dog the UK's withdrawal from the EU. Shipman's omission (or oversight) is emblematic of how and why Brexit has led to a constitutional crisis for the UK and produced a constitutional watershed for the island of Ireland. The critical failure by successive British governments to acknowledge or to understand fully the myriad complexities of the UK's departure from the EU, and its far-reaching political and economic implications for Northern Ireland in particular, created conditions under which some (as of yet undetermined) form of political and constitutional change now seems inevitable.

The 2016 referendum result forced “the Irish question” back to the centre of British politics, heralding a renewed interest in Northern Ireland in “mainland” Britain. Barely discussed during the referendum campaign, Northern Ireland and its border with the Republic of Ireland became the most complex, contested and vexing component of the Brexit withdrawal process (de Mars et al. 2018; Murphy 2018a; Cochrane 2020; McCall 2021).