This morning’s Times (£) reports that the Republic of Ireland, to the shock of British officials, has demanded that the Irish Sea be made its post-Brexit border with the United Kingdom.

The future of the Northern Irish border has been one of the major issues raised by the vote to leave the EU. London has been exploring ways by which it can use new technology to make post-Brexit border monitoring as unobtrusive as possible.

Instead the Irish Government of Leo Varadkar, the newly-installed Taoiseach who replaced Enda Kenny, is calling for both customs and immigration checks to be conducted at ports and airports. As the Times notes, this amount to “effectively drawing a new border in the Irish sea.”

Unionists are naturally aghast. Sir Jeffrey Donaldson, a senior Democratic Unionist MP, has pledged his party to blocking Dublin’s proposal in the Daily Telegraph. He points out that:

“Pragmatically that is just not going to happen. If you look at Northern Ireland, for example, out of the port of Belfast 73 per cent of the goods that come in and out of the port of Belfast which is by far our busiest port go to Great Britain. Why on earth would we want to create a customs arrangement between this part of the United Kingdom and the rest of the United Kingdom?”

This statistic illustrates a broader point which is too often overlooked or ignored by those hyping up the challenge posed by the border: Ulster is overwhelmingly more reliant on ‘cross-border’ trade with the mainland than it is with the Republic.

As I reported in May, Great Britain accounts for £13.8 billion of Northern Irish ‘exports’, against just £3.4 billion for the Republic of Ireland. Even treating Dublin as a gateway to the rest of the EU adds just a further £1.9 billion to that side of the scales, against the £3.8 billion from the rest of the non-EU world.

But Unionists have grounds for complaint about Varadkar’s bid to partially annex their Province beyond the much-overlooked economic logic of their place in the UK.

Although it is often mis-remembered as such, the ‘Peace Process’ was not simply a one-sided series of concessions by the UK. It also involved the Irish and nationalist side accepting the legitimacy of Northern Ireland and the Republic renouncing its long-asserted claim on the six counties.

Since the eclipse of the SDLP  as the major nationalist party in Northern Ireland this side of the equation has suffered – just try getting a Sinn Fein politician to talk about “Northern Ireland” rather than “the North” – but that party’s increasing prominence in the Republic seems to be pressuring Dublin politicians to echo its attitude.

It’s worth restating: Northern Ireland is part of our country, the United Kingdom, and is set to remain so until and unless a majority of its residents wish otherwise. So long as it wishes to remain British, the border is in the right place.

Varadkar can’t have the border moved into the Irish Sea until nationalists win a border poll – and forcing Ulster into a weird and highly anomalous situation where it faces passport and customs checks on its internal trade and movement in order to secure ‘frictionless’ access to a neighbouring state is not compatible with the respect for Northern Ireland’s current situation to which Dublin is pledged.

Not that criticism of the Irish Government’s new position is confined to the much-demonised DUP. Varadkar and Simon Coveney, his foreign minister, are taken to task in the Republic’s press too. Here’s one from the Irish Independent:

“So far, Coveney has made a dog’s dinner of Northern Ireland. Last week, Newton Emerson, the most moderate of commentators, asked why Coveney “was keeping the pot boiling”, referring to a series of cack-handed stances. But Coveney is not solely to blame. The buck stops with Leo Varadkar who weakly and wilfully gave him the job that Charlie Flanagan was doing well. The Taoiseach should clean up the mess he created by telling Coveney that Sunningdale taught Garret FitzGerald the dangers of pan-nationalist posturing. FitzGerald was finally forced to face the truth of O’Brien’s belief that what was good for Northern nationalist extremists was never good for Dublin.”

Sinn Fein, like separatists across our United Kingdom, have been deeply disappointed by Brexit’s failure to push many (if any) unionist voters towards the nationalist camp. This has only been exacerbated by the DUP’s dramatic electoral recovery at the general election, closing the window which seemed to open when Unionists lost their Stormont majority in the spring.

It makes sense for hard-line nationalists in these circumstances to engagement in brinkmanship and inject tension into the situation, in hope that uninterested and chronically under-informed mainland opinion can be shepherded towards concessions.

But the Irish Government should not fall into that bracket. Dublin’s steadfast refusal to reassess its own relationship with the EU in light of its dramatically changed circumstances makes this the very embodiment of have-your-cake-and-eat-it policy making.

Our own Government’s reliance on DUP votes, the Prime Minister’s clear view that we will leave “as one United Kingdom”, and London’s duty to uphold Ulster’s constitutional preferences all mean that we should expect a firm rejection of this proposal.