After Theresa May's disastrous week, you'd be forgiven for thinking her Brexit deal is dead – here's why you'd be wrong

Cabinet splits on Europe were embarrassingly exposed in last night’s Commons votes. Stephen Barclay, the Brexit secretary, was one of seven cabinet ministers to vote against delaying Brexit, minutes after urging MPs to support such a delay.

Theresa May, no longer able to paper over the cracks in her imploding cabinet, had to rely on the good sense of Labour and other opposition parties to win a majority for a delay; most Conservative MPs opposed her in a free vote. After such a farce, and another torrid week for May, you might assume her Brexit deal is dead. But in the looking glass world of UK politics, it is not.

A third vote on May’s agreement is expected next Tuesday. Her strategy for winning it is not just cynical; it is the height of cynicism. Why? Her EU negotiator Olly Robbins let this mangy cat out of the bag in a Brussels bar last month.

MPs thinking of backing the deal should remember the brilliant scoop by ITV News’s Angus Walker, who overheard Robbins saying: “Got to make [MPs] believe ... extension is possible, but if they don’t vote for the deal then the extension is a long one.”

It’s all coming true. Of course, May would rather have won this week’s vote than suffer a second humiliating defeat. But she knew she had a fallback plan, however desperate.

For it to work, she first requires the DUP to switch sides, to give Tory Eurosceptics cover to follow suit. So ministers are in intensive talks with the DUP – which, characteristically, wants to back down while claiming victory.

We should follow the money: the DUP’s “confidence and supply” agreement with the Tories, which resulted in an extra £1bn for Northern Ireland, runs out in June. Stand by for another bung if the DUP backs May’s deal, even if it is not announced immediately.

The DUP may win further guarantees that the province would not diverge from the rest of the UK on customs and regulations. It hopes that Geoffrey Cox, the attorney general, will miraculously rewrite his legal advice to say the UK might be able to use the Vienna Convention, which covers international treaties, to pull out of the Irish backstop on “change of circumstances” grounds if the EU made it permanent.

MPs such as Sir Edward Leigh have been banging on about this for months. Funny that Cox didn’t see fit to include it in the legal advice he sweated over until 5am on Tuesday, isn’t it? Other lawyers are sniffy: that such a “change of circumstances” is already widely discussed would hardly make it unforeseen.

The other threat aimed at Tory MPs is that a long delay would force the UK to take part in the European parliament elections in May. That would be a gift to Nigel Farage’s new Brexit Party. The weapon is not quite as powerful as it seems: if the EU and the government wanted to avoid elections in the UK, they could probably find a fix, such as current MEPs carrying on or MPs being nominated.

May is naturally throwing the kitchen sink at next week’s vote. We can hardly blame her. However, her problem is that she will probably need the support of about 25 Labour MPs to counteract a similar number of hardline Brexiteers who are unlikely to budge. Downing Street aides call them “the irreconcilables”. There was a time when 25 to 35 pro-Brexit Labour backbenchers might have rallied behind May’s agreement. But many of them now sense an opportunity to win a bigger prize – a softer Brexit, via a customs union.

If they scupper May’s deal, MPs will sooner or later hold indicative votes on a plan B and a customs union might well come top of the pile. That would be a much better course for the country than May’s unloved deal, not least for business. It would also help to solve the Irish border question.

EU leaders are understandably exasperated. They would no longer trust May to deliver a letter, let alone a promise. But they are unwittingly helping her deliver her own strategy by talking up the prospect of a long delay. The EU hopes this would create space for a UK rethink, so it might decide to remain after a Final Say referendum or general election.

But after last night’s votes, there is no guarantee of a Commons majority for a long delay.

So even if her deal is defeated a third time, the prime minister won’t give up. Next Thursday’s EU summit might then offer a long delay of up to 21 months. May could use that for a final attempt to browbeat Eurosceptics into line in a fourth vote just before the scheduled leaving date of 29 March. Just as Robbins predicted.