Now Labour, like EU, want to formalise the border pledge

Mr Marr asked Mr Davis whether that meant the government would back a mooted Labour Party amendment to write into law the impossibility of such a border.

“Let’s see what they write, shall we?” Mr Davis replied.

Yes, we must all do that. But the mere fact that Labour is talking about such an approach is telling.

When the EU tried recently to tie this matter down it did so by trying to ensure the ‘backstop’ arrangement would keep Northern Ireland in the customs union and single market.

This would mean a border in the Irish Sea. When Theresa May said no prime minister would accept such an situation, the Labour shadow Brexit secretary Sir Keir Starmer agreed it would be unacceptable for part of the UK to be detached so that it (in effect) remained in the EU while Great Britain left.

What then is he hoping to achieve by tying this down in legal text when even the EU itself has not yet managed to do so?

If Sir Keir’s party was showing genuine goodwill, then his intention would be to ensure both that NI continued to have unfettered access to the UK’s internal market and that the land border, where the regulatory divergence will begin, was as lightly marked as possible, so that we were all closer to everyone’s agreed outcome of an almost invisible border.

But until the wording of his suggested amendment is made public, there will be suspicion that this is merely an attempt to topple the government, as will happen if Labour’s suggested legal wording passes, and it has the same effect as the attempted wording of the EU. The DUP would have to quit.

In the meantime, this troubling matter remains uncertain, because London, while it sounds emphatic in its opposition to an Irish Sea border, has not put this opposition in the sort of concrete written and legal form that the EU and now Labour are insisting of the pledge not to have a hard border.