My sources say a no-deal Brexit is likely, but my head says there’s bound to be a deal. Which is right?

Betting markets say there is a 65 per cent chance of a withdrawal agreement that has to be agreed by the end of the month, Theresa May today told her cabinet

Perhaps the best thing to do with uncertainty is to describe it. No one knows what is going to happen about Brexit, so let us try to analyse why not. The basic problem is one of not knowing how people are going to behave in situations they can’t fully imagine.

We were in the same situation this time last year. No one knew what was going to happen during the critical talks to get through to the final stage of the negotiations. I was told by a government source that the chances of progress were “touch and go”, which turned out to be quite a good description of what happened. Theresa May came to the lectern in Brussels to say that the two sides needed more time on the Irish border question.

Her partners back home, the DUP, had objected at the last moment and she had to go back to negotiate with Arlene Foster, the DUP leader. Four days later, May was back in Brussels and the deal was done. The EU side announced that “sufficient progress” had been made and that the talks could now move on to the next stage.

Now we are in a state of unknowing again.

The betting markets say there is a 33 per cent chance of “no deal”. But what do they know? My best sources say that a no-deal Brexit is more likely than a deal. One of them has long said it is likely to happen by accident: each side will miscalculate the other side’s willingness to compromise until it is too late to pull back. Others say it is closer to 50-50, and that there is still a big gap between the two sides.

The trouble is that I don’t know whether to believe them. They said it was “touch and go” last year, and yet a deal was done. My head says a deal is almost certain to be done this time. If you stand back from the detail of the negotiations, the pressure for a deal seems irresistible. It is very much in Theresa May’s interest to avoid a disorderly Brexit; I think she would do it if she had to, and she would survive for a while – but her place in history would be wrecked.

Most of the other countries would rather do a deal, although the big players are not prepared to compromise the EU’s principles to do so. But Leo Varadkar, the Irish prime minister, has as much of an interest in a deal as May. He knows that if the UK leaves without a deal there will be a hard border across the island of Ireland.

And the enduring fact of British politics is that there is a majority for a soft Brexit in the House of Commons. My view is that, if there is a deal it would be approved by parliament, almost regardless of what is in it. That means it should be possible to agree that the UK will leave into an indefinite transition phase, during which nothing would change except that we lose our vote in the EU, and then negotiate a long-term trade relationship.

My problem, according to one of my friends, is that I “see politics in terms of rational self-interest”. Maybe. Or it may be that optimism is simply a human coping mechanism; I would rather not think about the difficult consequences for the country of leaving without agreement.

So yes. I don’t know. But I know quite a lot about why I don’t know. Which makes me feel better about not knowing.