Fintan O’Toole: Theresa May faces Irish obstacle on the Brexit tracks

Clio, the muse of history, has a wicked sense of humour. You can hear her cackling to herself these last few days: "What can I do to make the Brexit fantasia even nuttier? Ah yes – the return of the repressed! They recklessly ignored Ireland. Wouldn't it be such a laugh to leave their whole mad project at the mercy of a weird Irish party? What's this they're called? Hup, mup, dup?"

The internet exploded in the early hours of Saturday morning with anxious Brits frantically googling “Where is Northern Ireland?”, “What does DUP stand for?” and “Do they still believe in witchcraft over there?”

And it serves them right. Watching the Brexit campaigns last year, it was as if no one had heard of the Belfast Agreement. Ireland might as well have been Albania for all it seemed to matter. When the trade union leader Frances O'Grady raised it, the poor woman was obviously losing the plot – everyone quickly got back to serious questions like how to have one's cake and eat it.

So there is something delicious about the Brexit train having as its co-driver a party that hitched its wagon to it at least in part because of the lure of dark money channelled through sources with links to the Saudi government. And there is every chance that, if the DUP does manage to shore up Theresa May, it will drive the whole project off the rails. This would be no bad thing: Clio may have chosen a suitably crazy way to stop a crazy misadventure.

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EU priorities

The European Union has made clear its three priorities in the Brexit negotiations that will start next week: people, money and Ireland. People means the mutual recognition of the rights of EU citizens currently resident in the UK and Brits resident in the EU. It's doable.

Money means sorting out the divorce settlement and how much the UK will pay to meet its existing commitments to the EU budget. It will be a very bitter negotiation but it is doable.

Ireland means finding a way to honour the Belfast Agreement and prevent the recreation of a hard Border. It is not doable – with the DUP dictating terms on the British side of the table, it is an impossibility.

The DUP's bottom line has the virtue of clarity. Nigel Dodds spelled it out: the DUP will block any attempt to avoid a hard Border by giving Northern Ireland a "special status" within the EU. But to think that a hard Border can be avoided without a special status for Northern Ireland one must, to misquote the Queen in Through the Looking Glass, be prepared to believe three impossible things before breakfast.

The first impossibility is the idea that a soft Border can be achieved while Northern Ireland leaves the single market and the customs union. It is purest fantasy. The frictionless, fully lubricated Border, guaranteed to be free of chafing, rasping and abrasion, is an advertising slogan. It is not an actual proposition. If and when the UK leaves the single market and does its own trade deals with other countries, the EU and the UK will exist in radically different trading and regulatory regimes. No amount of technological wizardly or wishful thinking can make that reality disappear.

Border challenge

But the second impossibility is a hard Border. There is no default option of creating a standard international frontier. This is a matter of fact, not of opinion – a hard Border could not be created during the Troubles with watchtowers, troops and helicopters. It is certainly not going to be achieved with polite customs officers.

And in any case, the creation of this kind of border requires co-ordination on both sides. So let’s be clear in return: no Irish government will ever agree to its creation – and if the Irish government does not agree to it, the EU as a whole cannot do so either. No conventional EU frontier will be created on the island of Ireland because any Irish government has to stop it happening.

The third impossibility is that the Belfast Agreement be torn up. The biggest problem with the DUP’s insistence that Northern Ireland must not have special status is that it already does. The Belfast Agreement gives everyone in Northern Ireland an absolute right to Irish – and thus to EU – citizenship. This is a special status. And the EU has followed this logic by offering Northern Ireland a special Brexit. Unlike the rest of the UK, it has a return ticket – it can re-enter the EU unconditionally if it chooses to join with the Republic.

Now, in principle, Britain could simply withdraw from the Belfast Agreement and this is certainly the logic of the DUP's position. But if it unilaterally tears up the most important bilateral treaty in its postwar history, a treaty registered with the United Nations and guaranteed by the EU and the United States, what country in its right mind would enter the kind of bilateral trade deal on which Britain's post-Brexit future is predicated?

Cackling Clio has placed an Irish obstacle on the Brexit tracks. The choice has narrowed – all aboard for the trainwreck, or stop and think about taking a different line.