IT WAS a wise Irish civil servant who told me once, years ago, that the time to be afraid of British negotiators was when they offered a flurry of ideas. “Read them,” he said, “and you’ll notice one thing. They’re trying to trap you into discussing points of detail, so you end up ignoring the fundamentals.” His remark was made in the context of Anglo-Irish negotiations about the Northern Ireland peace process, but it applies just as much to Britain’s position in the Brexit negotiations, at least where Ireland is concerned. Their negotiating stance is based on an age-old truism — get them haggling about price, and they’ll forget the point of principle.

The good news is that the EU’s chief negotiator, Michel Barnier, and his team, saw the Brits coming. In a really astute report from Brussels the other night, RTÉ’s correspondent, Tony Connelly, pointed out that the Brits had published a 27-page paper full of technical suggestions about how you could have a border in Ireland, but that it wouldn’t really be a hard border. The EU had responded with a much shorter paper, refusing to engage with the technical stuff and pointing out that Britain had entirely ignored the fundamental issue of principle.

The principle is simple. After Brexit, any border in Ireland is a border between Britain and the EU. That border affects how people and goods come into and out of the EU. If Britain leave the EU and the customs union, then Britain, and by extension Northern Ireland, are on the other side of the border. Full stop.

Michel Barnier

But a border between Britain and the EU also, as a matter of law, becomes a border on the island of Ireland. The potential for damage of the re-emergence of a hard border on this island is huge. Even the British acknowledge that.

There’s no need to spell out the extent, and kind, of damage it could do. We’ve spent more than 20 years since the ceasefires and the Good Friday Agreement — which took violence from the conflict, but didn’t end it — trying to build a political process that could sustain itself and change hearts and minds. We know how fragile and faltering that is. The idea that you would re-insert a physical border into that equation is simply mind-boggling.

But Britain voted to leave Europe because it wants borders. It wants to control the movement of people. The largest single factor in the vote to leave was the fear of immigration. Controlling the movement of people is synonymous in the minds of Brexiteers with the language of regaining control of Britain’s destiny.

That’s why the British paper, which pretends that you can have a hard Brexit without hard borders, reminds me so much of the “angel papers” they used to produce during the Anglo-Irish negotiations.

They were called angel papers, and it was a British term, because they had no official standing. A paper could be produced full of the kind of language in which an agreement could be framed. But it would be presented as “random thoughts” or “musings”. If you didn’t like them, no harm done. If the British officials regretted offering them, or found they couldn’t sell them to their own political masters, they simply disappeared (I suppose, as an angel does, when his or her job is done).

But if you engaged with the stuff, you were trapped. What might be a flimsy idea on a bit of paper and have no standing could suddenly become something to beat you over the head with, if you gave it credibility.

The much wiser course was simply not to go there at all, until basic principles were agreed.

That, clearly, is what the EU has decided to do. They can see the impossibility, in principle as well as in practice, of agreeing to the re-imposition of a border on the island of Ireland. They know that if they agree to some technical tricks that make it look like something to which there is a “practical solution”, the issue of whether or not it is the right thing to do will become irretrievably muddied.

Sooner or later, in these negotiations, someone is going to mention the unmentionable. The British have decided to leave the EU. They’re pretending they can do so without creating a new border between them and the EU, and that that border will have to be situated in their neighbouring island.

That won’t work, and it can’t work. What needs to be said — and I’m surprised to hear myself saying this — is that in deciding to leave the EU, Britain has effectively decided that it is not possible to sustain the union between Northern Ireland and what it likes to call the mainland.

In short, the only logical solution to the issue of borders is for Britain to declare that it will, over time, withdraw from Northern Ireland. That, and that alone, would enable Britain to locate its border with the EU wherever it wants to, without doing untold damage to its nearest neighbour. Of course, the Brits may not be too worried about damaging Ireland, but it’s clear that the EU won’t allow them to undermine years of painstaking work on peace and political progress by playing jiggery-pokery with a border.

So, does that mean tiochfaidh ár lá? I don’t know, and it’s not from that perspective I’m saying it. But the only possible way for us to protect the interests of the people of this entire island is by declaring that there will be no border on the island, not under any circumstances. A border between Britain and the EU can only be achieved by Britain leaving Ireland.

That will certainly take years to work out , and would be an expensive operation, for both Britain and the EU. Britain is looking for a transition period anyway, in relation to customs arrangements. Part of that transition needs to be provision for full withdrawal.

The entire peace process was made possible, and is built on, the principle of consent. The principle of consent means that you honour the views that people express democratically.

The people of Northern Ireland voted to remain in the European Union. While the principle of consent was not conceived to apply to that circumstance, it is, nevertheless, the case that taking the people of Northern Ireland out of the EU, and rebuilding a border on the island of Ireland, flies in the face of any understanding of the notion of consent.

I think it comes down to this. We cannot allow a border to be built again on this island, for a myriad of reasons. Europe cannot be protected without one, but doesn’t want one, either.

Britain cannot have its cake and eat it. They must put their border elsewhere, and they must propose and facilitate whatever it takes to enable both parts of this island to remain within the EU.

In voting for Brexit, they effectively voted to leave Ireland. There is no other way forward.