There weren’t enough “personalities” in politics: that was what stand-up comedians used to complain during the Blair years. Gone were Margaret Thatcher, Michael Foot and Norman Tebbitt, the latter immortalised by his bovverboy Spitting Image puppet. In their place was a new managerial class of politician typified by Alun Milburn as health secretary (remember him? probably not), who were capable but so very dull.

Luckily there were some irreverent backbenchers to break the monotony. They turned up on shows like Have I Got News For You to inject raucous humour into bland stories. Affable ex-journalist Boris Johnson, with his guinea pig hair-do and rambling intellect, was one of them. To the unwary observer, he appeared to be out of the same stable as Gyles Brandreth, occupying the green benches more to gather material for a future TV career than out of serious political ambition.

How wrong that turned out to be. Well-disguised but steely personal ambition, twinned with a colossal sense of entitlement honed by Eton, Oxford and the Bullingdon Club, has brought Alexander Boris de Pfeffel Johnson to within reach of No 10. London City Hall wasn’t enough, nor was the Foreign Office (in spite of his gaffe-strewn tenure there demonstrating beyond all possible doubt his laughable unsuitability for high office). His intention to try and make himself 77th Prime Minister of the United Kingdom of Great Britain and Northern Ireland was dropped with calculated informality into a speech to insurance brokers on Thursday, no doubt delighting most of the 124,000 members of the Conservative Party on whose whim all our futures hang, while at the same time leaving millions of others wondering if it’s too late to emigrate.

It pretty much goes without saying that in the great game of constitutional chess being played out on the chequerboard of Great Britain, the prospect of a Boris Johnson premiership plays into the SNP’s hands. Left-leaning, moderate No voters – the very ones the SNP need to win over – are apt to find Johnson a serious turn-off.

But Boris Johnson in No 10 wouldn’t just boost the case for independence – it would be a humiliation in the eyes of the world.

Theresa May’s term in office has been accompanied by a collective cringe as Britain has become an international laughing stock, talking big about holding all the cards only to be outplayed by the other side. Other European leaders have watched Mrs May mishandle the negotiations with a mixture of schadenfreude, sympathy and embarrassment, like a class of students watching their peer mess up the end of term presentation.

Misguided in her strategy? Yes. Lacking in leadership qualities? For sure. Intransigent? Definitely. Mrs May is all those things. But few would deny that she has been doing what she thinks is right. To that extent, few question her integrity.

The trouble with Boris Johnson is that most people question his integrity.

Just consider the edited low lights. He was fired from an early job on The Times for making up a quote. He used a slur about black children and the term “watermelon smiles” referring to African people, in one of his columns. He accused Liverpudlians of “wallowing” in “victim status” over Hillsborough. He persistently claimed that leaving the EU would mean £350m a week for the NHS, even though it was demonstrably untrue. As Foreign Secretary, he worsened the plight of a vulnerable British woman, Nazanin Zaghari Ratcliffe, being held in Iran, when he wrongly said she had been teaching people journalism, thereby shoring up Iran’s excuse for holding her (it would have got him fired by a less abject prime minister). He sneeringly referred to women wearing niqabs as “letterboxes”, a move widely interpreted as a cynical attempt to appeal to the Tory right and which resulted in an upturn in Islamophobic jibes against women wearing the veil. Earlier this month, he tweeted that he’d just voted Conservative in the local elections, even though there were no local elections where he lives.

The list could go on, and on. What emerges is the impression of a man who has a loose relationship with the truth and a willingness to offend if he thinks his remarks will resonate with the right voters, a man who hungers after the status of high office but lacks a clear idea of what to do with it. Or as the First Minister Nicola Sturgeon put it, “a complete and utter charlatan”. What does he actually stand for? Famously, the self-styled head Brexiteer wrote two columns arguing for and against EU membership before coming out for Leave, supposedly to clarify his thoughts. No wonder he’s widely thought to have backed Leave as the best vehicle for his leadership ambitions.

He has been compared to Donald Trump, another populist big mouth. But while it’s embarrassing for the US to have a narcissistic reality TV star in the White House, it doesn’t change the economic, military and diplomatic status of the US as the world’s leading superpower. Britain by contrast is a country with a struggling economy in the twilight years of its global importance. By pursuing Brexit, Britain has all but squandered its enviable decades-old reputation as an open, pragmatic, level-headed and outward-looking country, by falling for nationalism, identity politics and anti-immigrant rhetoric. The election of Boris Johnson, a man widely regarded as a joke by the international community even before becoming foreign secretary, would signal to the rest of the world that the UK had well and truly lost its way.

Johnson must win enough support among Tory MPs to make it to the last two on the ballot, from which Conservative members choose a winner. He is not popular among his colleagues but his high recognition ratings may be enough for them to overlook his considerable shortcomings, as they may see him as the only candidate capable of beating Corbyn in a general election.

And so the needs of the Conservative Party once more seem likely to determine the UK’s fate. Now more than ever, Britain needs a skilled, far-sighted, trustworthy leader but it looks as if we might get Boris Johnson instead.