Here's a truth not yet universally acknowledged, Northern Ireland, the only part of the U.K. that has a land border with the European Union, ruinously complicates Britain's proposed Brexit withdrawal.

Simply put, there is no way to prevent significant border checks between Northern Ireland the Republic if the U.K. leaves the customs union, and that in turn has fateful and possibly fatal consequences for Ireland, north and south.

The Irish Taoiseach (Prime Minister) Leo Varadkar this week dismissed Prime Minister Theresa May's claim that a Canada-U.S. style border could be one potential solution. Speaking to reporters on Monday he said that idea was simply out of the question.

“I visited the Canada/U.S. border back in August and saw physical infrastructure with customs posts, people in uniforms with arms and dogs and that is definitely not a solution that we could possibly entertain,” he said.

In the Brexit supporting circles within the Conservative party that kind of insistence is received as Irish bloody mindedness, but they have yet to posit a border arrangement that does not seriously hamper free movement between the Republic and the North.

Citing the Canada-U.S. arrangement as a potential solution shows that neither May nor the Conservative party can successfully square their own circle. On the U.S. Side of the Canadian border, armed officers operate inspection posts including heavy duty truck X-Ray facilities.

The rules for persons crossing from Windsor, Canada into Detroit, USA who are transiting goods ensure they have to declare 23 data elements to 40 U.S. agencies. If that's frictionless, I would hate to see what the alternative is.

Before Brexit the Irish government strongly and repeatedly asked the British government to reflect on the dangers a EU withdrawal would pose to the peace process, the Good Friday Agreement and to the free movement of citizens, goods and services between the two jurisdictions on the one small island.

Those requests were unwisely and repeatedly ignored.

Now we are forced to watched as a slow motion train wreck piloted by the Conservative party and their enablers in the DUP threatens all of our futures and the fragile peace it took a generation to build. Trust us, they say, although they have made it clear they do not even trust each other.

I can't think of another time in its history when unionism has tried so hard to persuade us that its glaring political weaknesses actually amount to strength. In a moment that calls for reconciliation and partnership building they are instead doing what they have always done, circling the wagons against threats both real and imaginary.

But given that 58 percent of the citizens of Northern Ireland voted to remain within the European Union, the decision to counter the prevailing wish of their own jurisdiction seems a fatal one to me.

Many people in Northern Ireland appreciate the multiple identities that history has bequeathed them: Irish or partly Irish and/or British, and European. It was, until recently,  a moving buffet of identities and affiliations they could try on as the occasion demanded, and it suited the either/or cultural inheritance of the place.

But now that either/or choice is ending thanks to a projected future outside the European Union that will dramatically alter the relationship between the U.K and the Republic.

Now instead of consolidating the future of the union, instead of planning for its centenary, many within the unionist community are actually pondering its continued existence.

The majority unionist vote that consolidated its power since 1921 is effectively over. Now a border poll looks, thanks to political pushback over Brexit, like an inevitability.

Instead of consolidating unionist power, Brexit has undercut the rationale for maintaining the union in ways that they did not anticipate. In unwisely embracing this lamentable moment of flag waving British chauvinism, they have ultimately harmed their own political cause.

Brexit Northern Ireland

Brexit Northern Ireland

The facts are stark. May cannot withdraw from the single market and the Customs Union without creating the new border that both the Irish and Northern Irish governments dread.

Meanwhile the DUP, in their high profile moves to prevent marriage equality for LGBT citizens and their rejection of an Irish language act, daily demonstrate to their own weary constituents they still represent a backward looking, puritanical and often openly sectarian attitude to governance that the larger society desperately wants to escape.

The truth is the sudden rush in the U.K. and Northern Ireland to secure Irish passports after the vote tells us much more about Brexit's own internal weaknesses, and it tells us much more than just the cynical story of an anxious people looking to protect what they have just willingly or unwillingly surrendered.

But the most remarkable development of all, and frankly the most prophetic, is the newfound interest in Dublin in the plight of the Nationalists in the North. This is entirely new. Throughout the Troubles Nationalists were mostly a community surrendered to time. But in 2018 they have have been given a 'rock solid' guarantee by Dublin of no hard border, and that they will never be abandoned by the Republic again.

Dublin saw the irreconcilable contradictions of Brexit long before London did, in other words. They also see the potential outcomes very clearly now too.