Hold on a second, what if the Boris Johnson premiership turned out to be, actually, quite a good thing?

Doom and gloom stalk much of the Westminster establishment as they – we – await the seemingly inevitable elevation of Boris Johnson to prime minister. The buffoon, the crowd-pleaser, the cad, who has evaded responsibility his whole life, looks set to be swept into No 10 by the acclamation of provincial Brexiteers.

He may have won the support of more than half of all Conservative MPs, but nearly half opposed him with a passion. Former teachers, employers and colleagues have lined up to discredit him with their tales of “bad Boris”. The civil service, with the foreign office out front, can hardly conceal its loathing.

Even the decorous Theresa May chimed in, just hinting in her valedictory speech – no names named, just a swipe at those “making promises you cannot keep, just telling people what they want to hear” – that Boris Johnson was probably not her chosen successor.

And the doom mongers could be right. We could be in for a period of burbling, blustering, chaotic maladministration. Then again cheer up, chin up, we might not. Johnson at No 10 might not be the disaster you think.

Why not? Never one to disguise his ambition, prime minister is the job Boris Johnson has always wanted; his Churchill book hardly the subtlest clue. Three years ago, he dramatically abandoned his bid after a political lynching by Michael Gove. This time around, perhaps sensing that it is the last time the prize will be within his grasp, he has shown quite uncharacteristic restraint and discipline.

Now, that may reflect well on the influence of his – still? – girlfriend, Carrie Symonds, and her PR nous. But to convince Boris to get his hair cut, to tuck his shirt in, eat and drink less, not to throw out unguarded remarks, that’s quite a feat, and it suggests he wants the top job badly enough to keep himself under control – until that fateful night when the neighbours called the police to an apparent “domestic dispute”.

Then again, you might object, Boris was given his chance of a top job, at the foreign office, and failed dismally. Why on earth should he now be trusted with No 10?

But how bad a Foreign Secretary was he really? A large part of the foreign office was gunning for him as soon as he began. They did not like having a Leaver, let alone as risk-prone a Leaver as Johnson, as their boss. Johnson was also working under a prime minister with whom there had long been little meeting of minds.

Nor, crucially, was the job all it might have been. It was shorn of its most crucial portfolio. Europe, in the shape of the Brexit negotiations, was hived off to a new department before Johnson was allowed anywhere near the splendid office overlooking St James’s Park. He was also, it has been claimed and he denies, left out of the intelligence loop. Then someone was appointed chief negotiator who was patently unsuited for that role. Both the foreign office and Johnson, for their different reasons, might now think, not unreasonably, that the process might have gone better if they had been in charge.

Of course, none of that is any real excuse. Boris should have knuckled down and done as good a job with his “rest of world” brief as he could. He should have done his homework on Nazanin Zaghari-Ratcliffe imprisoned in Iran; he should never ever have compared the EU to Nazi Germany. He should have zipped his lips over what he was or was not told at Porton Down. He should not have called the French you-know-what, or tried to quote Kipling in Burma.

But might, under other circumstances, a breath of fresh air have been a good thing for the foreign office? Was his personal brand of diplomacy always a disaster? No; he has a charm and a social ease that generally travels well. And this, plus his broad political appeal, is what helped him to win two elections for mayor in a hugely cosmopolitan city whose politics is otherwise to the left.

He was not considered a bad mayor, either, as seen at the time. For all the condemnation now, in the heat of the Tory leadership contest, his supposed “vanity” projects – even the accursed Garden Bridge (that was actually driven by Joanna Lumley) – were popular.

The water cannon saga – bought in a panic, sold for a song – is a typical example of history written by the victors. He had a tussle with Theresa May, then home secretary, over buying them at all. But the reason was London’s abject lack of serious riot control equipment, exposed by the street violence of 2011. It was not as unreasonable a decision as it is now presented; their sale might yet be regretted.

As mayor, Boris was a well-recognised figurehead for the capital and a fount of ideas, from his proposed island airport to putting the north circular road underground. It was pesky administrators who stopped people getting on and off his new buses at the back, as generations of Londoners had done since there had been buses. And it was good riddance, thanks to Johnson, to the bendy buses that were prone to fires and totally unsuited to London’s roads.

To profligacy are now added laziness and irresponsibility as hallmarks of his time at City Hall. By and large, though, he appointed bright and competent people and expected them to do their job – and note how few of his then lieutenants have joined the anti-Boris campaign.

The ability to select good people and then delegate, to show some imagination, project a sense of identity, “sell” ideas, and tap into public concerns – all this is immediately transferable to the job of prime minister, while largely irrelevant for a foreign secretary. And we have plenty of examples from recent years, do we not, of people who could not do this.

Ah yes, the “character” question. There are many ways in which Boris Johnson is a thorough “bad-hat” (and worse). He has been sacked (twice) for lying, and bounced back as only the socially privileged and super-confident can.

But how many top politicians can be called, hand-on-heart, always 100 per cent honest, and is it a prerequisite for the job? It was a former top civil servant, remember, not a politician who admitted being “economical with the truth”.

And, yes, Boris Johnson has made the lives of some women, in particular, very difficult. But – again – if he is such a bounder, where are the myriad #metoo claims against him? After all, it is harder than it used to be to buy silence.

The still largely male-dominated political hierarchies may help to explain why what is loosely described as “womanising” has rarely been any sort of disqualification for high office. It is only when hypocrisy is added that private life seems to become a problem. Even, as it later transpired, John (back-to-basics) Major had an adulterous affair.

In a fortunate few, a combination of charm, a popular touch – and perhaps a certain unifying optimism are allowed to override dubious ethics or personal misbehaviour. You and I might regard this as reprehensible, but that is how it was, and is. It does not mean Boris Johnson will necessarily fail as prime minister.

In some ways, there is much about what Boris Johnson has done so far and how he has done it that could make him a very good PM, especially for current times. A prime minister does not have to master every detail, just the details he needs to know. Johnson’s popular appeal, his ability to delegate, his talent for “selling” a message, and his sense of hope could all work in his favour. He could just be the one to make the concessions and forge the compromises needed in the coming weeks.

And if not – well, he will learn, perhaps for the first time in his charmed life, that the buck stops here. As prime minister, he will have to take the blame and draw the consequences, and the country will learn that bluff, bluster and bonhomie do not a prime minister make. As of now, however, his unsuitability for the top job has not been proven. Boris could have exactly what this morose and divided country needs.