Brexiteers Ignored Ireland. Ireland May Have the Last Laugh.

A former staffer on the official campaign to persuade Britain to leave the European Union recently recalled an awkward moment from about a month before the Brexit referendum. The BBC’s flagship evening news program phoned the campaign’s offices in London to see whether someone would come on the show to debate the effects of Brexit on the Irish border — and no one wanted to do it.

Even the most able media performers felt “they simply lacked real knowledge of the issue,” the ex-staffer, Oliver Norgrove, recently wrote, in a column in the Irish Times. What’s more, the fate of the border seemed like a minor question: “I remember quite vividly the feeling of unease and discomfort about the prospect of us talking about something we just didn’t feel needed addressing,” Norgrove wrote.

In a classic case of the return of the repressed, the very question the supporters of Brexit refused to address has come back to haunt them. Theirs was a dream of a simple, once-and-for-all escape from the last 46 years of history. Britain would erase the recent past, in which its destiny has been intertwined with that of its continental neighbors, and begin a new and glorious story. But there is another history, one in which Britain has been entwined, for many centuries, with an even closer neighbor, Ireland. That story cannot be erased. And the impossibility of escaping from it has, in the end, made Brexit itself impossible.

If Brexit has come crashing down to earth, the piece of Earth in question is a straggling, meandering, perplexing and porous line on the map: the 310-mile long border between Northern Ireland and the Republic of Ireland. It emerged as a temporary line of partition in 1920 — ironically during another episode in which a country was exiting a larger union. Catholic Ireland was breaking away from the United Kingdom. The Protestant-dominated Northeast wanted to remain. So it was agreed that there would be a short-term boundary until a permanent solution was found.

That never happened. The temporary line became a permanent, fraught frontier. Irish nationalists regarded it with resentment as an improper imposition on the natural unity of the island. Unionists, on the other hand, regarded the border as their defense against being absorbed into a Catholic-dominated United Ireland against their will. During the 30-year conflict that wracked Northern Ire-land — between 1968 and 1998 — the border became one of the most heavily policed in the world, with armed troops, watchtowers and the buzz of military helicopters overhead. For the communities separated by it, it was a daily reminder of bitter and violent difference.

And then a wonderful thing happened. Britain, Ireland, the EU and the United States worked together to create one of the finest diplomatic achievements of the past 50 years: the Belfast Agreement of 1998. With peace, the border more or less vanished. The military and police installations were removed, and since both Ireland and the U.K. were in the EU, there was no need for customs posts either. For 20 years, people have come and gone freely over about 300 different crossings to work, trade and socialize — 105 million times a year. When I travel now from Dublin to Belfast, I struggle to remember where the border is — it is a line on a map, not a barrier on the road. It would be hard to overstate how much this has contributed to the sense of normality and the building of ordinary human contact that underpin the hard-won peace. A generation has grown up with this physical and psychological freedom.

But along came Brexit. Its effects, if implemented in their pure form, would be not just to restore a hard border between Northern Ireland and the Irish Republic but to make it much more extreme thvan it ever was before. It would now be a major EU land frontier: a boundary between the U.K. on the one side and a 27-member bloc on the other. This would be profoundly unsettling for a peace process that has made huge progress but is still fragile.

The naked truth is that the prospect of disrupting the peace agreement really does not matter to the voters in England who backed Brexit. Asked whether “the unraveling of the peace process in Northern Ireland” is a “price worth paying” for a Brexit that allows them to “take back control,” fully 83 percent of Leave voters agree that it is. This attitude reflects the recklessness of those who campaigned for Brexit, their blithe ignorance of and indifference to the consequences of what they were proposing. In this, the border question merely points to the broader reasons the whole Brexit project is such a dismal failure: It was never more than a set of slogans. It was all about the joy of exiting, with no clear sense of what condition the U.K. might be exiting into.

While Britain, which is the sovereign power in Northern Ireland, did not take its needs seriously, the EU did. For all its faults, the EU does understand itself as a peace project. What happens in Northern Ireland matters to its sense of Europe’s own identity. So the EU has fully backed Ireland in its insistence that there can be no hard border after Brexit. And this means that Northern Ireland (and hence the U.K. as a whole) has to remain aligned with the EU’s customs union and single market “unless and until” some other way of keeping the border invisible can be found. This so-called “backstop” is written in to the withdrawal agreement and has been, for the British, its most contentious aspect. It kills the fantasy of a clean break from recent history and makes Brexit a largely pointless exercise.

Their own culpable ignorance of Northern Ireland will not stop the Brexit zealots from blaming the Irish for the mess. In their eyes, Brexit would always have been a triumph were it not for the crazy complications of John Bull’s Other Island. Boris Johnson, who led the Leave campaign in 2016, has railed against the backstop as a “monstrosity” that “is being used to coerce the U.K. into becoming a vassal state of Brussels.” But if it is a monster, it is one conjured by the Brexiteers from the depths of their own rage against political and historical realities. Their willful delusions — regarding Northern Ireland, and much else besides — were always bordering on the insane.

Fintan O’Toole is a columnist with the Irish Times.