In the cloudy realms of unreality befogging this cabinet of fanatics, the approaching Brexit cataclysm is only “some bumps in the road”. So says Michael Gove, the minister in charge of national preparedness. True, austerity has inured the country to bumps: there are officially 7.8 million unfilled potholes, a £10bn backlog of repairs. But the earthshaking Operation Yellowhammer report is likely to cause something more like a seismic shock to public opinion on Brexit.

Corbyn's finest hour as the moderate compromiser would send his chances of winning the election soaring

Try as they might to dismiss this as some remainer plot, Yellowhammer is a professional assessment drawn up this very month for this government; drawn up for Boris Johnson and his hard Brexit cabinet. So hardly “old” and “out of date” as No 10 tried to claim. And this is what is most likely to happen – not a worst-case scenario. Dismissing it as “project fear” will only work with fingers-in-the-ears Brexit adamants: the public will be listening. If the cabinet refuses to believe these hard truths, they could sack the honest civil servants and find others who will tell the lies they prefer. Otherwise they must take this expert analysis seriously and turn back now.

If they ignore it, then we are ruled by politicians who have taken leave of their senses. Leaving the European Union on 31 October “by any means necessary” has become such a monomania that they no longer seem to care what happens on 1 November. Odder still, they no longer care that if just a few of these warnings are right the Brexit crash-out will render them and their party unelectable for a generation.

Jeremy Corbyn on Monday committed to calling a vote of no confidence within weeks, which could bring about a general election, so No 10 is warning any recalcitrant Tory MPs that their futures and their seats depend on Johnson winning that election. But talk to wiser Tories and they say growing numbers – now some 40 MPs – reckon their own survival and the very existence of their party depends on preventing Johnson charging straight over that no-deal precipice.

The Sunday Times is a Brexit-backing Murdoch paper, yet editors considered it a duty to splash on this doomsday document supplemented with page after page of hair-raising warnings. The Brexit-backing Mail published the “Secret dossier’s 14 claims of chaos” in similarly startling detail. This may mark an earthquake moment, when some sense of imminent national meltdown drove these media organisations to warn their readers of no-deal reality before it’s too late. If you want a conspiracy theory with an optimistic twist, might they be terrifying their Brexit readers to soften them up for a Johnson climbdown?

Play Video 3:05 Corbyn speech sets out Labour's vision for Britain – video highlights

Consider the scale of national disaster Johnson and Gove contemplate with apparent equanimity and you can only conclude we really are governed by lunatics, unless, just possibly, they still plan to spring some last-minute deal. Pause here to reprise the Yellowhammer analysis: ports chaos for three months and then only restored to 50% of their function; diabetics and children with cancer not guaranteed their drugs; no chemicals to treat the water supply; fresh food shortages; food riots; sterling plunging and banks disrupted; two refineries to possibly close, accompanied by strikes and fuel shortages; civil unrest around Ireland’s border before long; Gibraltar’s 15,000 workers delayed for hours daily at the border; embassies besieged by expat visa and passport worries; clashes at sea with our 12 vessels unable to police UK waters; care homes closing within months – and a lot more. Add to that the outrages which will be caused by Priti Patel’s hostile Home Office closing the border to Europeans on the stroke of midnight on 31 October: expect children separated from parents; doctors and nurses barred from returning to work; mayhem and scandal across Europe at our brutal behaviour.

Does this government really, truly, have faith that the people’s passion for Brexit – any Brexit – is so deep and so universal that most voters will judge these “bumps in the road” a price worth paying? Pollsters and focus-groupers warn that most of those true believers would rapidly melt away: mysteriously, overnight, not many will be found to admit to clipboard questioners that they ever voted to leave at all.

However delusional its thinking, the government does have one current advantage over its opponents: the “by any means necessary” single-mindedness that the remainers sorely lack.

One brief perusal of the Yellowhammer papers should be enough to knock the preciousness and sectarianism out of anti-Brexit MPs of all parties. Those who claim to put saving the country from no-deal Brexit above all other causes will be put to the test. Brave and, yes, noble rebels will risk their seats and their careers, risk breaking their party, breaking with lifelong friends and colleagues, losing part of their own identity: these things hurt. How odd that many say they are willing to make those life-changing sacrifices – but not to work, even very briefly, with Corbyn. That absurd sticking point suggests a loss of any sense of proportion, almost as crazed as the no-dealers themselves.

By all means let them list Corbyn’s defects and failings, the company he keeps, the things done and those left undone. His many equivocations on Brexit continue: on Monday he and John McDonnell were suggesting Labour take a neutral stand in a future referendum, a move that would be likely to drive away more Labour voters. Indeed, what an irony that Corbyn may yet be the one to lead the escape from Brexit. But he is leader of the opposition with 247 MPs. And he is not the bogeyman of Tory propaganda; the red demon about to turn Britain into Venezuela. All things are relative: absolutely nothing he or his manifesto ever proposed has approached the radicalism of the hard-right Brexit experiment this government is subjecting Britain to. Nothing in his broadly social-democratic plans has come close to the revolutionary explosion Johnson intends in 10 weeks’ time.

Holding their noses, if this is the only means, anti-Brexit MPs of all parties will need to back an interim government to delay article 50, call a referendum and/or an election. Corbyn should invite a cabinet of all parties to guarantee this emergency regime has no other aim.

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But if they balk, if they fail, then here is Corbyn’s chance to redeem his Brexit reputation, showing himself the best of them all by nominating someone who could command a majority – it hardly matters who. His finest hour as the moderate compromiser putting his country first when others refused would send his chances of winning the election soaring up in the polls. His strong speech in Corby etched out a policy-rich election pitch, with well-honed attacks on Johnson. His greatest fall in popularity has been due to his Brexit foot-dragging – so he has most to gain from genuine willingness to do “whatever it takes”, if that crunch comes. We shall see if he has it in him.

None of that drama may be needed if a majority of MPs succeed in their plan to halt Brexit by seizing control of the parliamentary timetable: the Speaker has pledged to ensure MPs are not overruled. But if they fail and at the last hour, the only salvation for the country is the extraordinary prospect of Tory MPs holding their noses and backing Corbyn, that’s what they must do. And if they lack the necessary patriotism, then let Corbyn show them how it’s done.

• Polly Toynbee is a Guardian columnist