After the no-deal Brexit horror show – what if there is a deal after all?

Let us try to imagine what might happen four months from now. It is Tuesday 18 December, a week before Christmas, and the House of Commons faces a vote on the EU withdrawal deal finally agreed by Theresa May in Brussels the previous weekend.

It is hard to predict what might be in that deal. Indeed, it may not be clear at the time. The language may be fudged and important questions may be left to be negotiated during the transition period after our departure.

But let us suppose that the prime minister secures a deal. After the no-deal Brexit horror show that has been running all summer, this may seem childishly optimistic, but it is the holidays and we all need some escapism.

Also, I may have been too long in the sun, but I thought I detected a different tone from Michel Barnier, the EU’s chief negotiator, on Tuesday. He repeated a phrase he used earlier this month, saying he was sure the EU and the UK could build a partnership that is “unprecedented” in scope and depth. That implies some flexibility in the EU’s rules-bound approach.

Let us look at the possible timetable. The Brexit deal was supposed to be finalised at the October EU Council – one of the formal meetings, four times a year, of the heads of government of all member states. But that deadline is slipping: Barnier hinted at a possible informal summit in November, while David Lidington, the cabinet office minister, said he thought there would need to be an agreement “by the end of 2018”. Lidington is important because, though he doesn’t hold the title of deputy prime minister or first secretary of state, he is May’s deputy in the engine-room of government, the cabinet committees.

Let us assume, then, that the deal is done at the EU Council scheduled for Thursday and Friday, 13 and 14 December. Quite possibly, the talks would run overnight into Saturday. But then a tired and triumphant prime minister would return to seek the approval of the Commons, sitting for four days the following week before rising for Christmas.

If the Commons voted to approve the deal, it would then be voted on by the European Parliament, which is sitting 14-17 January. Its assent cannot be taken for granted, but if the EU’s leaders have signed up to it, it is likely to be forthcoming.

But what would happen in the House of Commons if Theresa May came to it with a deal? How would parliament exercise its legal right, gained for the first time, to veto an international treaty? This was discussed at length during Dominic Grieve’s struggle to define the meaning of a “meaningful vote” in the EU (Withdrawal) Act while that legislation was going through parliament.

When it comes to it, though, it may be that MPs face a simple choice. It would be the deal or leaving with no deal, with all the disruption and cost that we now know that implies. I suspect that there would be no third option. Postponement; renegotiation; another referendum: I doubt that there would be a majority in the Commons for any of them.

It almost doesn’t matter what the deal is – that it has been agreed could transform opinion. The hard Brexiteers will hate it, obviously, whatever it is. But most Remainers would probably clamber gratefully on board the lifeboat to save them from the dystopian disaster of a BLT famine and stockpiled medicines.

Keir Starmer, the shadow Brexit secretary, repeated this week that Labour would vote against a deal that failed the tests he has set out. I think we would find that, if there were a deal, it would miraculously meet Labour’s tests. I cannot see Jeremy Corbyn and Starmer going into the division lobby with Jacob Rees-Mogg and Boris Johnson to vote for a no-deal Brexit.

The question, then, is how many MPs do Rees-Mogg and Johnson have behind them. This week’s letter from Rees-Mogg to Conservative associations urging them to “chuck Chequers” (he’s the son of a journalist, you know), was alleged to be signed by 62 MPs, although no list has been published. If so, that means Rees-Mogg has lost five followers since a similar letter was published in February, also signed by 62 MPs, because since then five Tories have resigned from government positions to oppose the negotiating position set out at Chequers.

In the end, the Labour leadership or enough Labour backbenchers would find a way of ensuring that May’s deal is approved. If need be, it would be like Roy Jenkins in 1972 leading 69 Labour MPs, including Roy Hattersley and John Smith, to vote against the whip to support Britain’s entry into Europe.

I think that, if Theresa May secured a deal, almost any deal, it would be approved by parliament.

The other thing that negotiating a deal would do, is to transform the prime minister’s standing and her place in history. But that is for another day.