Can Theresa May fix Brexit border problem?

But as we left Brussels in the pitch black this morning we're still in the dark about what happens next, and how Theresa May can get this whole process back on track, and smartish.

While it's not the end of the potential overall deal if the two sides can't move on to the next phase of talks at the summit next week, it is what both sides desperately want.

The longer it takes, the more risk there is of course of other parts of yesterday's draft being unpicked. The idea was, remember, to lock in the agreement so far, then get on with the rest. It isn't clear what happens next though.

There are some big political and practical questions to ask. (If you are not very interested in the minutiae of all of this, look away now.... but guess what, it's not just about a fight with her allies in Northern Ireland, but her friends and rivals around the cabinet table too).

There is a dispute over whether or not they had seen the full text of the draft agreement yesterday.

Some sources say they hadn't seen the whole thing, therefore they hadn't seen the full context of what was being said, and flew off the handle over the initial leaks from Brussels over what had been agreed, the UK government "conceding" on the border as MEPs outside the Commission building told us before May even arrived.

While it's clear the DUP was in close contact with the government it is possible to believe they hadn't seen the whole text complete with the caveats, because even senior officials involved in the talks weren't allowed to have electronic copies of the document, only hard copies.

And as there had been lots and lots of changes to the text over the weekend, it's not impossible to imagine that the final, final, final version that then emerged had not been shown in full to the DUP.

Others in government suggest the DUP had seen it all, and as we reported last night, the Tory chief whip told the PM it was all signed off. If that's the case, it is a much bigger political problem of trust for the PM, if the DUP had been kept in the loop and given their approval, but then threw their toys out of the pram.

It's not clear whether the PM and Arlene Foster will meet in the next couple of days in person, but from late last night talks between the two sides were under way.

But with such strong objections on the record now, it is very difficult to see how the DUP can just say, ok then prime minister, when we said we couldn't back it, we really meant that we could, unless there is a change in the language in the text that has already taken weeks of painful negotiation to agree. It's said there are three different policy options that could provide a fix, but this feels more like a battle of wills.

And don't forget, there are a number of Tory MPs who agree with them. The idea of close "alignment", is anathema to some Conservative Brexiteers too.

There is however a very big difference between allowing Northern Ireland to choose to keep cooperating in some sectors and write that into the deal, and imposing a much bigger change where it essentially stands alone from the rest of the UK, and is pushed much closer to the EU.

2. This morning it feels pretty much impossible for the other side, Dublin, to back down in any way.

Irish leader Leo Varadkar, who is in the middle of a political whirlwind of his own, went public yesterday to make it clear that there was indeed an agreed text, and that there was no way that it could be unpicked.

Beyond the reassurances on policy that the Irish so desired, to change tack politically and suddenly give back the concessions that appear to have been so hard won seems extremely unlikely to happen.