On June 5, there were audible gasps in the House of Commons in London. The UK parliament was discussing the anomaly of the realm’s abortion laws: while Britain legalized abortion in 1967, Northern Ireland, though subject to the same parliament, still operates under an extremely restrictive Victorian-era law banning all abortions unless the mother’s life or health is at serious risk. The subject has recently come to the fore because the Republic of Ireland’s landslide vote last month to repeal its constitutional ban on abortion has made the situation in Northern Ireland seem all the more egregious.

Heidi Allen, a Conservative member of parliament for an English constituency, had just given a highly personal and emotional speech in favor of change:

I was ill when I made the incredibly hard decision to have a termination. I was having seizures every day. I was not even able to control my own body, let alone care for a new life. Are you telling me that, in a civilized world, rape, incest or a fetus so badly deformed it could never live, is not sufficient grounds for a woman to decide for herself? No. Enough.

Allen was immediately followed by the veteran Democratic Unionist Party MP Sammy Wilson. It was he who caused the sharp intakes of breath when he defended Northern Ireland’s effective ban on abortion by arguing that it had resulted in the birth of people who, “if we had had the legislation which exists here in the rest of the United Kingdom, would have been discarded and put in a bin before they were ever born.”

Allen and Wilson are, in principle, firm allies. Wilson is one of the DUP’s ten MPs who are propping up Prime Minister Theresa May’s minority government. Allies often disagree, of course, but they tend not to gasp in horror at each other’s attitudes and values. This was one of those moments when fault lines, usually convenient to ignore, suddenly crack open. These particular lines run through the idea of Britishness itself, and the fissures therefore inevitably extend into the currently dominant expression of that idea: the Brexit project.

The DUP is, strictly speaking, not a British party at all: it organizes and contests elections only in Northern Ireland, where it has become the largest party on the Protestant and Unionist side of the divide. But its raison d’être is the preservation of the “British” identity and political allegiance among those in Northern Ireland—and therefore the maintenance of Northern Ireland’s place within the United Kingdom. Yet the DUP’s Britishness is increasingly out of kilter with Britain itself. This is a decidedly unbalanced love affair in which most of the ardor is on one side. What the DUP thinks of as an indissoluble bond is, for British Conservatives, a marriage of convenience.

There are two underlying problems. One is religion. Historically speaking, there is no doubt that English and, later, British identity pivoted on Protestantism. The collective “us” was defined in opposition to a “them” that was primarily Catholic: Catholic Spain, Catholic France, Catholic rebels in Ireland and Scotland. The DUP’s own mindset is completely in accord with this Protestant formation. Its history is militantly anti-Catholic, and though it tries to play this down nowadays, the reality of Northern Ireland’s sectarian divide is that Democratic Unionists still see themselves facing off against a growing and increasingly assertive Catholic minority.

But England is now an outstandingly irreligious country. In a 2016 survey, 53 percent of all adults in England and Wales described themselves as having no religious affiliation whatsoever. A mere 15 percent considered themselves to belong to the established Anglican church. This Anglican church is, moreover, rather like its official head, Queen Elizabeth II: mild, cautious, vaguely benign. It would be unfair to say that the Anglicans put the pale into Episcopalianism, but let’s just say their supplies of brimstone are fairly low. Theresa May, for example, makes a lot of her origins as an Anglican vicar’s daughter but she does not make much of herself as a Protestant prime minister. A century ago, the Church of England was, with some justice, described as “the Conservative Party at prayer,” but religious values are more conspicuous by their absence than by their influence in May’s Tory party.

In its DNA, the DUP was always somewhat at odds with this mildly religious expression of Britishness. It now attracts significant support from members of the Irish episcopal Protestant church (known as the Church of Ireland), but its roots are in hard-line evangelical Presbyterianism. The party’s founder, the Reverend Ian Paisley, was a fiery preacher who would denounce the pope as “the anti-Christ” in fifty different ways. One of his signature campaigns, launched in 1977 to try to stop the decriminalization of homosexuality in Northern Ireland, was conducted under the slogan “Save Ulster from Sodomy.”

This Episcopalian/Presbyterian divide did not ultimately matter very much—so long as Britishness could reasonably be understood as quintessentially Protestant. Northern Ireland—ironically, with the support of the Catholic Church, which is dominant in the nationalist community—could remain a reservation of social conservatism within a rapidly liberalizing UK. But, as those gasps in the House of Commons so clearly indicated, the religious dimension of official Britishness has dwindled almost to nothing. This is indeed one of the great differences between British and American conservatism, even between the Trump and Brexit phenomena: Christian fervor is no longer a major force in British or English conservatism. The DUP is now much closer to the Christian right in the US than it is to mainstream Protestantism in Britain.

The other problem for the DUP is the rise of a specifically English nationalism. English conservatism has long seen the preservation of the Union, including Northern Ireland, as a definitive goal: May’s party, after all, is officially still called the Conservative and Unionist Party. But the Brexit project has shown this commitment to be much stronger in rhetoric than in reality. Both Scotland and Northern Ireland voted decisively against leaving the EU. The Brexiteers are willing to go much further than just ignoring the wishes of those populations; it is clear that if Brexit were to lead to an independent Scotland and a United Ireland, its proponents would see these outcomes as prices worth paying. This makes sense: Brexit is, above all, an English national revolution—and its imagined act of liberation would be all the purer if it resulted in an independent English state.

For the DUP, though, this would be disastrous. The party enthusiastically supported Brexit but did so, one suspects, in the confident belief that it would never happen. The DUP’s Brexit campaign was a day trip to a British theme park, a chance to wave the Union flag and to be clasped warmly to the bosoms of those in the Conservative Party who welcomed any allies they could get in the glorious cause of overthrowing the imaginary oppressor in Brussels.

But actually winning the referendum was not supposed to happen because it creates existential problems for Northern Irish Unionism. These include not just the problem of the Irish border—the insuperable contradiction between the requirement of the 1998 Good Friday peace agreement for a porous border and the European Union’s need for a hard border with post-Brexit Britain—but also the even deeper folly of upsetting the careful balance created by that 1998 peace agreement. All the pre-Brexit evidence was that Unionism had been doing quite well out of that agreement: Catholics, no longer disgruntled, now assured of equal treatment and a share in power after many decades of feeling like second-class citizens, were making their peace with life in Northern Ireland and postponing the dream of Irish unity indefinitely into the future. Brexit, by wrenching them out of the EU against their will, forces them to raise once again all the large questions of long-term national identity that had been successfully suspended.

Objectively, therefore, Brexit is a disaster for the DUP. But the freak result of the UK’s general election last year has concealed this truth under a blanket of apparent power. Even while its long-term goals are being undermined, the party has ascended into a heaven of Britishness, holding the balance of power not in Belfast but in the heart of the mother country. The thrill has been so electrifying that the party scarcely notices that it is getting burned. Nor does it notice, except perhaps when it hears those gasps at a bald statement of its anti-abortion position, how deeply its Britishness is out of sync even with Conservative British opinion.

Here, then, is the great dilemma for the Brexiteers. To salvage something from Brexit, the DUP has to be able to say that it used its influence over Theresa May to stop her from making any deal with Brussels that would weaken the Union (of Northern Ireland, England, Wales, and Scotland). But there is only one deal with Brussels that does not weaken the Union, and that is one in which the UK as a whole stays at least in the customs union (which allows goods to move around the EU without tariffs) and probably in parts of the single market (which removes almost all regulatory barriers). This is the very deal that the Brexiteers denounce as a fundamental betrayal of their whole project of “taking back control” from Brussels. If, as the Irish government and the EU as a whole insist must be the case, there is to be no hard border on the island of Ireland after Brexit, then Northern Ireland has to become a special zone that effectively stays within the current EU regime. But if, as the DUP insists, Northern Ireland can be treated no differently from the rest of the UK, then all of the UK must stay largely within that regime. In which case, Brexit itself becomes pointless.

And so, in a final irony, the DUP’s backward-looking Britishness stands in the way of Brexit’s English revolution. It is a conundrum that will eventually elicit not gasps of horror but groans of agony.