Theresa May’s single most important strategic mistake

Before the big vote on Tuesday night, the EU’s 27 government heads will provide greater reassurances – probably in the form of a collective letter to Theresa May, and within the mandate confirmed at the last EU Council – that the controversial Northern Ireland backstop will not and cannot be forever.

What does that mean?

Well for those MPs agonising about whether or not to support the PM’s Brexit plan, and who think the word of political leaders counts for something, a few votes may move in Theresa May’s direction.

And maybe, in the words of one senior British minister, May will be able to frame the letter as being both ‘substantive’ and ‘legally’ significant.

But it will not sway the vast majority of her critics, because the Withdrawal Agreement will not be re-opened – and whatever the letter’s legal force it could not trump the international treaty that is the Withdrawal Agreement, so there will be no legally binding guarantee that the backstop will fall away by any specified date.