“We are getting close to resolving this now.” So Philip Hammond told the BBC’s Andrew Marr today, delivering this fabulously silly Brexit forecast without a flicker of visible irony. Who says the chancellor doesn’t have a sense of humour? As it happens, he went on to break character pretty quickly by admitting that there may not even be a third meaningful vote on Theresa May’s deal this week.

If the government’s managers do not think they have a chance of winning – or at least of significantly reducing the margin of defeat – they will not subject the prime minister to yet another humiliation on Tuesday. The case for trying is the remarkable speed with which a number of previously hardline Brexiteers are discovering the merits of pragmatism and reconciliation. It is amazing how quickly non-negotiable objections can melt away as the clock ticks, reality bites and careerism trumps principle.

It is also worth mentioning that Tories are, and have always been, disproportionately worried by the verdict of posterity. When How the Conservatives Went Mad as a Box of Frogs (2016-30) by Prof Gyles Pittiless is published, none of the Brexiteers want starring roles as the culprits who took the most electorally successful party in modern history and turned it into a factory for idiocy, magical thinking and introspective nativism.

Even so, the task of turning a 149-vote defeat into victory (or something close to it) remains colossal. There is something ignominious about the way in which the attorney general, Geoffrey Cox – notionally a custodian of impartial legal advice – has become the prime minister’s chief huckster, deployed to persuade the Democratic Unionist party and the European Research Group that the Irish border backstop is (contrary to his previous guidance) nothing to worry about.

Especially desperate has been his invocation of the Vienna convention on the law of treaties. It is quite true that this agreement enables nations to abdicate treaty responsibilities when there has been “a fundamental change of circumstances”. But the jurisprudential bar for such a change is (as you might expect) extremely high: if the UK were overwhelmed by bubonic plague or climatic disaster, for instance, it could legitimately invoke the convention to seek exemption from, say, its routine Nato obligations; being really cross about the backstop probably wouldn’t cut it.

No Brexiters want to be the culprits who took the most electorally successful party in modern history and turned it into a factory for idiocy

At any rate, this shoddy campaign of persuasion continues. Hammond conspicuously failed to deny Marr’s suggestion that more public money was being offered to the DUP to oil the wheels of the third meaningful vote. What is certain – and publicly admitted – is that the whips’ numbers do not suggest that victory is even close in what, as part of the continuing effort to make Brexit incomprehensible, has become known as MV3.

Jeremy Corbyn, for his part, shot down reports he was preparing to throw a lifeline to May by backing the ingenious amendment devised by the Labour MPs Peter Kyle and Phil Wilson, which would attach House of Commons approval of the prime minister’s deal to a subsequent public vote. (In other words, MPs would support the withdrawal agreement but give the electorate the final say.)

Unfortunately for May, this is not what Corbyn has in mind at all. In an interview with Sophy Ridge on Sky News, the Labour leader was explicit that he would countenance a people’s vote only on a “credible” deal – which is to say a Labour Brexit. He also made clear, when pressed by Ridge, that, in such a referendum, he would vote for Brexit: an important admission of a position that has long been suspected but never publicly declared.

So for May, the overwhelming likelihood is that she will arrive at this week’s European council as supplicant – having failed to secure parliamentary approval for her deal, and seeking an extension of article 50. The question is: on what terms, and for how long? On duration, May might find an unlikely ally in Martin Selmayr, the European commission’s secretary general - who favours an even shorter delay than the three months presently mooted as a bare minimum. Why, Selmayr asks, risk institutional paralysis within the EU?

A very short extension would enable her to return to the Commons, give a couple more weeks, and present them with a brutal choice, the one she has always preferred: my deal or no deal.

It is more likely, however, that the EU will insist upon a deferral of three months, and possibly much longer. As Donald Tusk’s spokesman said last week, our 27 partners will demand “a credible justification for a possible extension and its duration”.

Facebook Twitter Pinterest Theresa May with Donald Tusk during the EU leaders’ summit to finalise the Brexit agreement in November. Photograph: Reuters

This is, of course, the best approach by far. The hardening British orthodoxy – that we just need to get past Brexit and move on to other issues – reflects a bogus premise: that the withdrawal agreement is essentially the end of the matter. In fact, it is only the beginning of what will be an agonisingly protracted process of further negotiation, legislation and technical argument. To rush through May’s deal would be like cutting corners when building the foundations of a house because you want to move in quickly.

More time – and plenty of it – is exactly what we need: to consider calmly and deliberatively the various configurations of Brexit on offer, to judge whether any of them are worth pursuing, and then to put the least-worst option to the people in a referendum.

Whatever happens, we are in for a lot more Brexit. But the resolution that Hammond offers is phoney. The real choice is between a nation still connected to the world – with a chance of prosperity, growth and global relevance – and one reduced to counting haggard unicorns across a horizon of self-inflicted decline.

• Matthew d’Ancona is a Guardian columnist