The Brexit stalemate dates back to last December's backstop

Theresa May certainly seems to have alarmed the recipients of her missive, Arlene Foster and Nigel Dodds.

But, at those two leaders of the DUP acknowledged yesterday, the detail remains unclear.

We will all have to wait until it becomes clearer.

The difficulties and stalemate all date back to last December’s backstop.

It is widely agreed, even at the highest levels of the Conservative Party, that the implications of that agreement with the EU were not fully understood. It is even suggested by some informed commentators that Ireland did not fully understand the possible constitutional implications, and so was not engaged in any land grab over Northern Ireland.

If the UK is retreating from a permanent, NI-specific backstop, then that is a massive breakthrough.

If it isn’t, and is prepared to concede in legal text provisions that have the effect of ensuring the Province can never significantly diverge at any time from Great Britain in terms of regulations or tariff policy, then it will become very important indeed that the government is defeated when it brings its deal with Brussels back to MPs.