It’s the defining issue of Brexit, but who understands Northern Ireland?

Have you ever visited Northern Ireland? You should go – it’s a fascinating place. In fact, if it were less fascinating – that is to say, less complicated – then the UK’s departure from the EU would have been easier. You have that to thank us, or resent us, for.

Before you visit you should familiarise yourself with some of the basic geography. First of all, where is Northern Ireland? Obviously it’s in Ireland, but only in one version of Ireland. It is on the island of Ireland, but not in the political state legally named Ireland. So it’s in Britain? Not quite, it is not on the island of Britain but it is in the United Kingdom – the state often referred to as Britain. It can therefore be described as being in both Britain and Ireland, one politically and the other physically. But unpack that sentence further: it is not on the island of Britain or in the state of Ireland. It is neither and both at the same time.

Northern Ireland is defined by its wanting to be in two places at once but not really being in either. Which is fitting, because while Northern Ireland is the defining issue of Brexit, it is also strangely absent from the debate. It is the elephant in the room, but other than the elephantine DUP and their unsubtle supporting turn in this fiasco, ministers, MPs, journalists, and assorted pundits (remainers and leavers alike), spend a vanishingly small amount of time actually trying to understand it. Or why the EU, at its philosophical core a peace project, might feel emboldened to act on behalf of a region that is only relatively recently at peace, and still without true reconciliation.

That brings us to the backstop, a noun now invariably prefaced with “controversial” or even “hated”. But hated by whom? Certainly by the DUP and the European Research Group, but for different reasons: the DUP because the backstop countenances the prospect of Northern Ireland being treated differently from Britain in certain ways. The ERG says it, too, is greatly affronted by this, but some people – particularly people actually from Northern Ireland – take this claim with large portions of salt. It seems likely that the UK-wide elements of the backstop, keeping the UK in a near-customs union, are what really bothers Brexiteers, rather than the principle of Northern Ireland diverging. But the backstop only covers the whole UK at the British government’s request, an attempt to salve the fears of the DUP. An attempt that has not worked.

Again, we arrive at the question: where is Northern Ireland? It may be in the UK, but that fact is remarkably easy to forget in London, where most parts of the establishment struggle to locate it in their mental conception of the place they govern. Some see that obliviousness as malign, but if it is, it is sort of understandable. None of the major UK parties organise in Northern Ireland in a significant way (the Tories stand but get a derisory vote). Its obscure concerns and tribal psychology are baffling.

A backstop is required to ensure there is no hard border in Ireland if a comprehensive free trade deal cannot be signed before the end of 2020. Theresa May has proposed to the EU that the whole of the UK would remain in the customs union after Brexit, but Brussels has said it needs more time to evaluate the proposal.

As a result, the EU insists on having its own backstop - the backstop to the backstop - which would mean Northern Ireland would remain in the single market and customs union in the absence of a free trade deal, prompting fierce objections from Conservative hard Brexiters and the DUP, which props up her government.

That prompted May to propose a country-wide alternative in which the whole of the UK would remain in parts of the customs union after Brexit.

“The EU still requires a ‘backstop to the backstop’ – effectively an insurance policy for the insurance policy. And they want this to be the Northern Ireland-only solution that they had previously proposed,” May told MPs.

Raising the stakes, the prime minister said the EU’s insistence amounted to a threat to the constitution of the UK: “We have been clear that we cannot agree to anything that threatens the integrity of our United Kingdom,” she added.

I worked on Brexit in Downing Street before and after the EU referendum. I droned on about Northern Ireland’s predicament, but it was impossible to place it at the front of anyone’s mind until it was forced there by the EU. This obliviousness is not limited to politicians, but extends to the media and broader commentariat. In late 2016, the Stormont executive began falling apart over renewables subsidies, but also because of the toxic effect of Brexit on relations between the parties. At the time I had a bet with a colleague about how long it would take for Downing Street to be questioned about power-sharing falling apart at the daily lobby briefing of journalists. If the DUP hadn’t found itself holding the balance of power after the 2017 election, we might still be waiting.

Even now, Northern Ireland is not so much discussed in the media or parliament as referred to: “backstop” and “border” being code for “problem”, with limited discussion of what the problem is, or why it requires a solution. Again, some of this is understandable, Northern Ireland’s complexity is wearying. But wearying too is the repeated failure in London to note something fundamental: that the majority of people in Northern Ireland appear to support the backstop, despite the opposition of the DUP.

Northern Ireland Screen maintains a digital archive of old film, one of which is a tourist promotion feature from the 1950s, the halcyon days of the old Unionist-controlled Stormont parliament. Aimed at the English market, an upper-class young woman named Anne tells viewers of the beauty of the Giant’s Causeway and the Mourne mountains. And of the warmth of the people of “Ulster”, or “Alsta”, as she pronounces it in her clipped RP accent. As the camera pans out over the Irish sea, she bids her unnamed correspondent a final thought on Northern Ireland: “A place which is strangely different, almost a foreign country.” Almost.

• Matthew O’Toole is a former No 10 Brexit spokesperson; he works for Powerscourt communications group