Confirmation that the EU will use the border as a wedge

By proposing a common regulatory area between Northern Ireland and the EU, Mrs May told the House of Commons that it threatened the constitutional integrity of the United Kingdom.

The EU, as this column noted yesterday, now views the Irish border as a vulnerable point in the British negotiations. Brussels knows that the Tory government is fragile and that Downing Street is reluctant to so much as introduce direct rule for fear of offending nationalists, such are the raw political sensitivities now.

It knows also that it has Dublin on board for the toughest possible negotiating line against the UK in these talks.

Mrs May’s robust response, therefore, is welcome.

But it also raises a number of questions: why, then, was such an outline text agreed in December (and why did some unionists hail it at the time?) in which every effort was made to reassure Dublin that there was no possibility of a hard border? Such a commitment has been seized fully by the EU, and was the precursor to yesterday’s provocative document.

It also raises from a unionist perspective the urgent query: what would the position have been if the UK had not been propped up by the DUP? The initial form of EU-UK wording in December, which was rejected outright by that party, suggested that a standalone Tory government would have fully succumbed to the Dublin-EU axis.

So the DUP, by a fluke of parliamentary arithmetic, has prevented a border in the Irish Sea. But the DUP is unlikely to be able to stop this on its own.

This is a major political battle in which any voices who oppose a border in the Irish Sea, and an obstacle to internal UK trade, need to make themselves heard. There are still many powerful people at Westminster across the political spectrum who support an unfettered internal UK common market.