Dante and Beatrice. Quasimodo and Esmeralda. Cyrano and Roxane. Don Quixote and Esmeralda. These unrequited loves have great poignancy. But they’ve nothing on the tenderest, most poignant tale of unrequited love in our times, the tragically one-sided crush the DUP has on Britain.

It is one thing to be infatuated with someone who just ignores you. The unfulfilled love retains its bittersweet purity, its dreamy half-life of pure possibility. But the true tragedy occurs when your love is apparently consummated at last and you find that the loved one really despises you. The DUP has long dreamed of being wrapped fully in the warm embrace of the Tory world with which it strives so hard to identify. And now, miraculously, its moment has come. But the loved one is thinking of England, sneaking glances at her watch and praying “Oh god! When will this be over?”

Ian Paisley "was many things but no one could ever seriously think of him as a Brit". The DUP used to be unionist but not really British. Ian Paisley was many things but no one could ever seriously think of him as a Brit. His touchstones were fundamentalist Presbyterian dissent and the place he called Ulster. Its hinterland was Calvinist Scotland, not Westminster.

Moment of destiny The problem, of course, is that the holiday turned out to be a semi-permanent relocation. The DUP was surely as perplexed as Boris Johnson was when the jolly jaunt to imperial nostalgia turned into a moment of destiny. The day trippers to Little Britain found out that there was no return train and that they were stranded on a beach far from reality with the tide of bad news slowly but relentlessly coming in. That’s not Land of Hope and Glory playing on the Tannoy – it’s Hotel California.

Then British prime minister Margaret Thatcher "said in 1981 that Northern Ireland is as British as her own constituency of Finchley". File photograph: ITV/Rex The other problem is that Northern Ireland, Paisley’s beloved Ulster, voted emphatically against Brexit. And this, paradoxically, has forced the DUP to double down on its besotted Britishness. It can justify ignoring the democratic wishes of the polity it actually leads only by reviving a notorious line from Margaret Thatcher. She said in 1981 that Northern Ireland is as British as her own constituency of Finchley. The DUP has to claim that Northern Ireland is as British as Lambeth or Edinburgh – it doesn’t matter that they all voted Remain because they are merely parts of the greater British whole.

This is nonsense, of course. Northern Ireland is not as British as Finchley and Brexit dramatises the difference: it is not the absolute right of the residents of Finchley to remain citizens of the European Union after Brexit. But it is, for the DUP, a necessary nonsense. It has to remain frozen in an absurd ultra-British posture that even Thatcher abandoned when she signed the Anglo-Irish Agreement in 1985.

Contradiction The infatuation mires the DUP in a hopeless contradiction. Because it wants to be super-British, its manifesto in the Westminster election commits it to a hard Brexit, including exit from the customs union. But because it is actually an Irish political party, it really wants a soft Border. And these two desires are utterly incompatible. You can leave a customs union or you can remain within an arrangement where no customs barriers apply. You can’t do both.

DUP leader Arlene Foster: Her party "is, at last, a British political party, a key player in the Westminster game. Its hour has come." File photograph: Niall Carson/PA Wire The fortunes of electoral arithmetic have now given the DUP’s pretence a weird moment of apparent validation. It is, at last, a British political party, a key player in the Westminster game. Its hour has come. But does it notice that, even as the Tory party clasps it to its bosom, the lack of enthusiasm would be scarcely less evident if the Tories were wearing rubber gloves and surgical masks? They are not swooning with love, they are fainting with revulsion. The DUP may think it is coming home; most Tories think the mad woman has come out of the attic of an old hyper-Protestant British identity and is sitting in the parlour demanding tea and scones with lots of jam and a bucket of clotted cream. She has to be humoured for now, but only until there is some way to get rid of her.