How does Boris Johnson solve Brexit now?

The first and most important task facing the new prime minister is to get Britain out of the EU by 31 October – so what is the plan, and will it work?

Does Boris Johnson have a plan to get Britain out of the EU? If he does, it is likely to fail, which would mean that on 1 November we will still be in the EU and our new prime minister may well be announcing a general election – saying parliament has blocked him and he needs a new mandate to finish the job.

That seems the most likely outcome to me, but let us go through the Johnson government’s Brexit challenge step by step to test our assumptions and to see what other paths history might follow.

The first assumption is that Johnson will try to renegotiate the withdrawal agreement, but that he won’t obtain significant changes. This isn’t because the EU side is inflexible, although it is, but because there is no easy solution to the problem of the Irish border.

The EU wants a guarantee of an open border between Northern Ireland and the Republic, and a guarantee implies some way of holding the UK to its word. Hence the terms of what is known as the backstop, which can be ended only by agreement of both sides – an arrangement described as vassalage by the Brexit purists who sabotaged Theresa May’s deal.

Maybe the EU side will agree a time limit to the arrangement, or a relaxed definition of an open border, with checks being carried out some distance away, in the expectation that the technology to make it work will be invented in time. But why, if they couldn’t agree something with May, should they agree it with Johnson, of whom they generally have a lower opinion?

One possibility is that, if the EU thought the UK would leave without a deal, it might have an incentive to compromise, because it would fear there would be a hard border in Ireland anyway.

Here we come to our second assumption, which is that Johnson won’t be able to take the UK out without a deal. EU leaders cannot be sure about this – after all, Johnson has just been elected by the Conservative Party on an absolute promise to take Britain out of the EU, deal or no deal, on 31 October.

But I think it will become increasingly clear that parliament would block a no-deal Brexit. Philip Hammond, the outgoing chancellor, told Andrew Marr on Sunday: “I am confident that parliament does have a way of preventing a no-deal exit on 31 October.”

The first step is to prevent the new prime minister suspending parliament, which is close to being achieved by amendments to the Northern Ireland (Executive Formation) Bill.

Parliament could then legislate, as it did in April, to require the prime minister to seek a Brexit extension if it has not approved a deal by a certain date. That seems likely to be where we will get to: if Johnson presents the House of Commons with essentially the same deal as May, I think it will be rejected again.

Johnson might think about trying to escape the law by failing to agree an extension, but in the end I think the majority in the Commons against a no-deal exit will exert itself.

Its ultimate sanction would be to bring Johnson’s government down in a vote of confidence. As Hammond said, “I don’t think it will get to that.” Like the nuclear deterrent, the threat is designed to be credible but never to be used.

I think there are enough Conservative MPs, including former ministers, who would vote against Johnson on a motion of no confidence if they had to. The plan would be not to have an election straight away, but to install a caretaker prime minister who would ask for an extension. Because the threat would be credible, Johnson would be forced to seek an extension himself in order to stay in office.

This brings us to our third assumption: that EU leaders would grant a further extension. One of them could veto it and decide to force us out. Johnson could even say to Emmanuel Macron, “Bon ami, do me a favour and stand your ground; refuse an extension.”

If the French president did so, large numbers of Labour MPs would probably vote for any deal rather than take responsibility for either a no-deal Brexit or for revoking Article 50, which would be the only other choices.

However, I don’t think Macron would do it. He threatened to last time and backed down. When it comes to it, EU leaders don’t want to decide Brexit for us if we can’t decide it ourselves. So I think they will give us more time.

This leads to our fourth and final assumption, that Johnson would then fight an election asking for a mandate to take us out, deal or no deal. He may think that Jeremy Corbyn is weak, and that Nigel Farage can be held at bay. I am told that Farage thinks Johnson will have to do a deal with him, and is looking forward to discussing terms.

An election certainly seems a better prospect for Johnson than two and a half years of miserable failure to deliver Brexit until certain defeat in 2022. His other main option would be a referendum.

I think a second referendum is possible, but the problem is, as ever, what the question would be. If Johnson has rebadged May’s deal, it could be a straight choice between that and Remain, with parliament committed to enacting the result. But with parts of the Tory party infected with no-deal Brexit fever, and Labour increasingly moving back to its Remain equilibrium, it is not clear how the legislation for a referendum would get through the present parliament.

So I think the most likely outcome – this is probability rather than prediction – is an extension in October, followed by a general election.