Johnson will leave scorched earth. The idea that he should stay until autumn is madness

The end, if it has indeed now come, was more graceless even than we could have imagined. Boris Johnson did not seem sorry. Not now, maybe not ever. When the Downing Street limpet was finally chiselled off his rock, it was only to deliver a parting salvo lacking in all humility or self-awareness but instead verging on the accusatory.

The prime minister thanked the millions of voters who trusted his party, without acknowledging that he had gleefully spaffed that trust up the wall for two-and-a-half long years. Instead he called his colleagues “eccentric” for wanting to ditch him now, just when everything was going so brilliantly, unless of course you count the lying and the unchecked sexual predators and the crumbling public services and the grinding poverty. Johnson degraded the country he was elected to serve, and his legacy will be long painful years of fixing the damage done to almost every aspect of national life. Yet still, he wanted his supporters to feel that if anything, he’s the real victim here. That “poor me” note is a dangerous one for a departing prime minister to strike in febrile times.

When this nightmare is finally over – which will arguably be when he finally surrenders the keys to No 10 – the Conservative party owes this country an apology. It should hang its head with shame for foisting on us a man so unfit for office that he had to be dragged from it kicking and screaming and threatening to burn everything to the ground. It should apologise for choosing a leader it knew to be a lightweight and a liar, who broke the law by partying through lockdown yet still reportedly thinks it appropriate to stage one last bash at Chequers on his way out. But it should apologise, too, for underestimating what he was capable of when cornered, or how hard he would be to remove. Having apologised, it should not expect simply to be forgiven.

What seemingly persuaded Johnson to unchain himself from the No 10 radiators was the prospect of staying as caretaker prime minister until autumn, while a successor is chosen. But that would be madness, as Tory MPs are falling over themselves to point out. Convention may dictate that a prime minister who loses a vote of confidence carries on running the country, for the sake of continuity, until a successor is chosen. But doing so requires sensitivity, diplomacy and the ability to put people’s needs above your own. Who imagines Johnson capable of that? He’d rather take his enemies down with him, leaving nothing but scorched earth. He may even still fantasise on some level about something happening that allows him to try to un-resign. At the very least he’ll meddle in the leadership contest, hating the idea of someone else succeeding where he failed.

Fresh crisis looms for the union, given his continued authority is unlikely to be meekly accepted in Scotland and Wales and will be virtually nonexistent in Brussels, where this government is supposed to be negotiating Northern Ireland’s post-Brexit future.

Meanwhile the prospect of him spending the summer trying to line up lucrative gigs for his political retirement seems unconscionable, given the powers of patronage that would still be at his disposal and his history of seeming none too fussy about who pays for the gold wallpaper.

And more prosaically for his party, the longer he stays, the more the scandals keep coming. Even in his final hours he conceded that as foreign secretary he had met the former KGB agent Alexander Lebedev, the father of his friend (and the then owner of the Evening Standard) Evgeny Lebedev, without officials present in Italy at a time of high tensions with Moscow. This is the man we want to leave in charge of national security over summer?

But that’s not all. Johnson’s insistence on clinging to power long after it was tenable brought us frighteningly close to the brink. In his final hours he was visibly positioning himself to go full Trump, arguing that he was the people’s choice and only they can fire him. So far, he has stopped short of attempting to mobilise the deranged strand of rightwing populism that constantly fears its Brexit is about to be stolen in some deep state Remainer plot. The tone of that resignation speech, with its odd references to parliamentary “herd instinct” moving against him, will however ring real alarm bells for some Tories.

Too paranoid? Maybe. The cabinet emerging from Thursday morning’s surreal reshuffle looks slightly more grownup than expected – whatever you make of their agendas, the likes of the new levelling up secretary, Greg Clark, or the new Welsh secretary, Robert Buckland, are capable of at least ensuring the wheels don’t fall off – although the junior ranks will probably be more chaotic. Johnson himself might find it prudent to slink off early, before the parliamentary inquiry into whether he lied to MPs over partygate concludes. But to believe this cabinet capable of restraining Johnson is to ignore, as John Major pointed out, the last one’s failure to do so. Major is right that there are only two options: either Johnson goes instantly and his deputy, Dominic Raab, becomes caretaker, or the process of choosing a successor must be drastically sped up, perhaps by removing grassroots members’ say in it.

At the very least, the Conservative party must now organise the swiftest succession possible, coalescing quickly around a successor rather than plodding through an endless summer of hustings while a vacuum develops at the top. Meanwhile Whitehall, the devolved governments and the main parties must put together a plan B that does not rely on Johnson doing the decent thing – which should include opposition readiness to trigger a parliament-wide vote of no confidence, if necessary, to oust him. British institutions cannot keep expecting Johnson to respond like a normal politician and then being surprised when it doesn’t happen.

Related: Boris Johnson will resign as Tories insist ‘reckless’ prime minister must go now – live updates

A general election to put this squalid and chaotic government out of its misery is now wildly overdue – though it will have to wait for Durham police to issue their verdict on Keir Starmer. Finally, Brexiter Tories must keep stressing that ditching Johnson was not some factional coup but a decision that united leavers and remainers. Leadership candidates must leave no opening for anyone, in or out of the Conservative party, to whip up the kind of toxic emotion that led to the thuggish harassment of remain-voting public figures during critical Brexit votes. The Conservative party created this monster. They shouldn’t underestimate how hard it may be to stop.

• Gaby Hinsliff is a Guardian columnist

• Guardian Newsroom: Boris Johnson resigns
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