No-deal is better than a bad deal was Theresa May’s mantra for two years, making clear that Britain would walk away from negotiations with the EU if necessary.
Her statement after the marathon cabinet meeting on Tuesday night, however, put paid to that.
In a move which threatened to split her party always something she had sought to avoid Mrs May dramatically changed strategy and announced she would seek a deal with Labour support.
What changed her mind? I have been told by government insiders and those close to the prime minister that the answer is the UK union.
One of her inner circle said: She’s fixated on the union. No-deal clearly puts huge strain on the Irish border and the consequence of that is a border poll becomes a real possibility.
She thinks it would be high risk and if it succeeded there would be a great impetus to Scotland. It could be that serious in terms of the breakup of the UK.
Two other government sources told Sky News they believed the union was the decisive factor in Mrs May’s thinking.
Northern Ireland, it warns, would require direct rule for the first time since 2007.
The Assembly at Stormont has not sat for two years, with civil servants running day-to-day operations.
But decisions about security in a no-deal situation would need to be made by government ministers, Mrs May was warned.
The Good Friday Agreement 1998 sets out the conditions for a referendum on Irish reunification. Just 36 Tory MPs backed a customs union relationship with the EU in indicative votes last week.
A training session held for Tory MPs on Monday about what a customs union is was attended by just 45 MPs.
Meanwhile more than 170 MPs signed a letter to Theresa May last weekend saying she should go for no deal if her withdrawal agreement fails in Parliament.