For the better part of two decades, the importance of the internal Irish border was steadily diminishing. After the Good Friday Agreement of 1998, customs posts were dismantled, checkpoints removed, and for ordinary people the crossing from Newry to Dundalk, or from Derry to Donegal, became as unremarkable as crossing from Ohio into Pennsylvania.
The triumph of the Agreement was not only political but spatial: it rendered a line drawn in 1921 invisible. That invisibility was symbolic of peace, of compromise, of a settlement in which Irish unity could be pursued constitutionally, Unionism could be respected, and the European Union could be credited as the silent engineer of harmony.
Until Brexit brought a sudden end to that rosy-hued vision.
When ministers and MPs began discussing the United Kingdom’s departure from the European Union, Ireland was an afterthought. The debate centred on sovereignty, trade with distant continents, and the practical implications of “taking back control”.
Only belatedly did British politicians realise that Brexit would necessitate the erection of a customs frontier somewhere. That frontier could lie on the island of Ireland, between North and South, or in the Irish Sea, between Britain and Northern Ireland. Either way, one of the United Kingdom’s foundational bargains—the union of its four constituent parts or the settlement between nationalists and Unionists in the North—would be strained to breaking point.
The most immediate political effect of Brexit was to make the border a live question again.
For years, the constitutional status of Northern Ireland had been insulated by the principle of consent stipulated by the Good Friday Agreement. Northern Ireland would remain in the UK unless a majority voted otherwise. And Dublin would not interfere.
With the EU as a common framework, the distinction between North and South was softened. The daily lived experience of Irish citizens in border regions was one of fluidity: shopping in Newry, working in Monaghan, holidaying without thought of passports.
Brexit threatened to undo this carefully nurtured normalcy.
The prospect of customs checks, tariffs, or even physical infrastructure along the border was immediately recognised as a potential provocation. Nationalists feared a return to visible partition; Unionists insisted that the North’s place in the UK must be honoured.
Brexit elevated the European Union from background actor to central arbiter of Irish affairs. The EU’s solidarity with Dublin during negotiations was near total. For once, Ireland was not the supplicant but the ally whose cause aligned with European principles. Brussels, defending the integrity of its single market, also became the guarantor of the Good Friday Agreement.
With London sidelined, it was Brussels that led the way. The EU helped broker the Northern Ireland Protocol, a compromise that placed the customs frontier not on the island but in the Irish Sea. Goods entering Northern Ireland from Britain would be checked, keeping the border with the Republic open and Northern Ireland effectively within the EU single market for goods.
This solved one problem but created another. Unionists saw the Protocol as an existential betrayal, a severing of Northern Ireland from the rest of the UK. Nationalists, by contrast, saw it as confirmation that the island’s economy was converging and that the old barriers were crumbling.
This is how Brexit turned the Irish border from a fading relic into the sharpest political dividing line in decades.
Sinn Féin could present itself as both the defender of the Good Friday Agreement and an advocate for eventual unification. Meanwhile, the DUP, having initially championed Brexit, found itself trapped by its consequences—defending a union that was eroded by the very project it had supported. The politics of Northern Ireland, once paralysed by the weary routines of power-sharing, suddenly shifted back to the constitutional question with a vengeance.
The economic effects of Brexit were just as dramatic, though often less visible, gradually widening a structural divergence between North and South.
For the Irish Republic, Brexit required a massive reorientation of trade. For decades, the UK had been its main partner. After 2016, though, Dublin accelerated diversification toward continental Europe and North America. Infrastructure investments—new ferry routes to France and Spain, expanded ports, logistical corridors—were fast-tracked in order to bypass dependence on British “land bridge” transit. Ireland thus emerged from Brexit bruised but with a more assertively European identity.
Northern Ireland’s position was far stranger. Its citizens had departed the European Union against its will, with 56 per cent of voters supporting Remain in the 2016 referendum. The Protocol kept it inside the EU single market for goods, granting it a unique status: simultaneously bound to the UK and integrated into the EU. This paradoxical circumstance created friction with Britain, but it also brought advantages for Northern Ireland’s trade with the Republic.
Businesses in Northern Ireland enjoyed preferential access to both markets. Some firms quietly thrived, exploiting their hybrid position. However, Unionist anger, focused on the symbolic affront of enduring checkpoints at the ports of Larne and Belfast, often drowned out discussion of these economic benefits.
The asymmetry in outcomes was striking. The Irish Republic, once dependent on Britain, grew closer to Europe; Northern Ireland, once aligned with Britain, found itself economically converging with the South.
Brexit thus deepened integration between North and South even as it reignited political division. For farmers, manufacturers, and service providers straddling the border, this was not a theoretical debate but lived reality. Supply chains had to be reconfigured, regulations aligned, paperwork mastered. What Brussels and London had negotiated in the sterile language of treaties was experienced with visceral intensity in border counties as delays, costs, and occasional opportunities.
Brexit didn’t just transform politics and economics; it transformed identities.
For nationalists in the North, the argument for unity gained new resonance. If remaining part of the UK would mean isolation from Europe and cumbersome trade relations with their neighbours, why not consider integration with the Republic, now framed as the European, modern, prosperous option?
For Unionists, by contrast, Brexit represented a double betrayal: first, that their British identity had been devalued by London’s willingness to treat Northern Ireland as a bargaining chip; second, that they had been politically marginalised for having opposed the Protocol but lacking the leverage to overturn it.
Brexit’s impact on the younger generation was more acute. Polling suggested that younger Northern Irish voters—especially Catholics, but also a significant minority of Protestants—were more open to constitutional change. The pragmatic appeal of EU membership, Erasmus programs, and the cultural capital that accrues from being “European” resonated strongly for them. For many young people, unity was less about nationalism than access to opportunity, as they enviously compared the Irish Republic’s booming technology sector and cosmopolitan cities with Northern Ireland’s often stagnant economy.
At the same time, Brexit also complicated identity in subtler ways. The Good Friday Agreement had allowed people to be Irish, British, or both. Brexit disrupted this pluralism. Individuals with Irish passports could still travel freely, work in Europe, and feel part of a broader community. By contrast, those relying solely on UK passports faced new restrictions.
The inequality of mobility was immediately palpable. In border communities, where mixed families are common, this could mean siblings with different rights depending on which passport they held. The supposed simplicity of “taking back control” thus fractured daily life in ways both petty and profound.
Brexit also strained the political institutions of Northern Ireland. The power-sharing arrangements at Stormont, fragile at the best of times, collapsed under the weight of disputes over the Protocol. Unionists refused to return to government until their concerns were addressed; Nationalists insisted that the Protocol was essential to peace. This impasse led to a prolonged suspension of devolved government, leaving civil servants to manage budgets while public services deteriorated.
This paralysis had direct consequences for the relationship between North and South. The North–South Ministerial Council, a body designed by the Good Friday Agreement to encourage cooperation, languished. Cross-border initiatives in health, infrastructure, and education slowed. Dublin, wary of being accused of interference, trod carefully. Meanwhile, public frustration at the spectacle of ungoverned institutions surged.
The irony was sharp: Brexit, framed in London as an assertion of sovereignty, eroded Northern Ireland’s capacity for self-government. The Irish Republic seemed stable by comparison, reinforcing its appeal as partner and counterweight. The asymmetry in institutional functionality—Dáil Éireann humming along, Stormont silent—sent its own political message.
Brexit also reopened deeper cultural wounds. The border, long suppressed as an issue, re-emerged in public consciousness. No longer was it merely a technical matter of trade routes and customs paperwork, as was the case prior to the referendum, but the fulcrum for a profound political, social, and economic realignment. Murals, parades, and commemorations began to resonate more forcefully. Cultural symbols became battlefields: the Union Jack on lampposts, the Irish tricolour on murals, and EU flags waved at rallies.
For nationalists, the Northern Ireland Protocol symbolised the slow but steady erosion of partition. For Unionists, it stood for abandonment.
In the long arc of history, Brexit may be remembered less for its slogans about sovereignty than for its unintended consequences. It made the invisible border visible again, not as a line of checkpoints but as the central dilemma of a shared island.
The relationship between North and South is now irrevocably altered. Whether this leads to integration, instability, or some new equilibrium remains to be seen. But one thing is clear: the border that disappeared after 1998 has, thanks to Brexit, returned—not in physical form, but in politics, economics, and memory.
Photograph courtesy of Allan Leonard. Published under a Creative Commons license.
