A warning from the former leader of Northern Ireland that a referendum is looming on the province's place inside the United Kingdom has exposed the pressures thrown up by Brexit on British territorial integrity.
Peter Robinson, who led the Democratic Unionist Party and was first minister for eight years, said opponents of reunification must make preparations for a vote. Under the 1998 Good Friday Agreement, the British government can trigger a Yes or No vote on Irish unification if officials believe there is a groundswell of support for the move.
In the 20 years since the landmark peace deal there has never been a majority in polls for unification.
But with uncertainty and division clouding London's negotiations over the UK's exit from the European Union the status of Northern Ireland has become a major sticking point.
Inside the region there are growing calls for a vote that would in effect keep it in the EU.
Mr Robinson warned his fellow unionists that a so-called border poll was the elephant in the room for supporters of the status quo.
"Pulling a paper bag over our heads and thinking that we can, thereby, close out the impending danger is crazy," he wrote last week.
Unionist politicians reacted with dismay, accusing their former leader of acting as an echo chamber for Irish nationalists. The row led his successor as party leader, Arlene Foster, to defend Mr Robinson's right to speak.
Sammy Wilson, a Westminster MP and de facto spokesman for the hardline wing of the DUP, said the intervention signalled defeatism.
"It is not enough to say that a referendum is coming so prepare the terms in case we lose," he said. "Churchill knew that the Nazis were coming after Britain when they defeated France in 1940 but he didn't prepare terms for the event of a successful invasion. He rallied the people by telling them to prepare to fight on the beaches and in the laneways and in the streets and to never surrender.
"That's a far better strategy and that is what I am hearing from unionists who I speak to and who are alarmed at the talk of an inevitable referendum and the possibility of losing it."
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Jim Wells, another DUP representative, also questioned the wisdom of unleashing a constitutional debate when other issues were pressing like Brexit and the restoration of the devolved government, suspended since 2016. "The issue had been put to bed," he said. "What's facing the party leadership at the moment is so complex and so time-consuming that, really, we shouldn't have to worry about what former leading lights in the party have said."
But a former Downing St aide to Theresa May said Mr Robinson was pressing on a new faultline in the island's politics. "Even if you leave the Border aside, the messy implementation of Brexit has self-evidently weakened the United Kingdom. Since sustaining the union depends on the consent of both moderate nationalists and the constitutionally agnostic, making the UK less rich and less attractive risks a swing electorate that has little emotional attachment to the union," wrote Matthew O'Toole, who quit the British government last year.
Yet many in the north feel that even if Brexit is disastrous for the regional economy, there is still little likelihood that reunification would happen.
Kevin Skelton, a man who lost two relatives in the 1998 Omagh bombing which killed 29 people, said Dublin would not be capable of underwriting the costs of unity. "The south of Ireland doesn’t want us, doesn’t need us and can’t afford us," he said. "If the vote was held on both sides of the Border they'd likely reject us."
Sinn Fein, the largest nationalist party, has also taken a cautious stance. Mary Lou McDonald, its leader, told a weekend rally that conditions would eventually dictate a vote. "We are entering a defining period of Irish history,” she said. “Change is coming and it must be managed sensitively and imaginatively."