On 12 October, Boris Johnson held a press conference at the Foreign Office in London with Witold Waszczykowski, his Polish counterpart. Dressed in a dark suit and looking – for him – quite smart, the Foreign Secretary stood at the lectern and recalled how the Poles had helped Britain fight “the cruellest tyrannies of the 20th century – fascism and communism”. He stressed Britain’s “unconditional and immovable commitment” to Europe’s defence and security and claimed, Brexit notwithstanding, “Today the British and Polish peoples are more closely connected than ever before.”

It took a journalist from the Polish Press Agency to puncture Johnson’s “pleasantries”. He said that a million Poles now feared for their future in Britain. They felt as if they were on the Titanic, with everyone promising to rescue them but no lifeboat in sight.

In response, Johnson assured Britain’s Poles that they were “here to stay”. He then blamed Britain’s European partners for the continuing uncertainty over the status of EU citizens living in this country, accusing them of ignoring the UK’s overtures. “Some of the urgency you direct at me I would radiate backwards and ricochet it to our friends and partners in Brussels,” he said, in the colourful, mildly humorous language that he routinely deploys to deflect awkward questions.

At no point did Johnson acknowledge any personal responsibility for the Poles’ plight, or for the xenophobic tinge of the Leave campaign that he led last year, or for the demands of his fellow Brexiteers for tough new immigration controls. He doesn’t do gloom – just optimism, however baseless or unrealistic, which is one reason that few people in the world of diplomacy and international affairs take him seriously.

Indeed, most are appalled by his apparent failure to address the pressing international issues of the day; by the gratuitous offence that he has given to so many of the UK’s partners when it desperately needs their goodwill; and by the country’s loss of stature on the global stage.

Chris Patten – a former EU external affairs commissioner, Hong Kong governor and Conservative cabinet minister – was scathing about Johnson when we spoke. “If you were concerned about the principles and vision and long-term interests of Britain, you would not regard him as your pin-up,” he said. “This is an office once held by people like Carrington, Hurd, Douglas-Home, Callaghan and Bevin. What on Earth has become of us?”

Nigel Sheinwald, a former ambassador to the US and the European Union, told me: “His [Johnson’s] style gets in the way of handling foreign relations in a serious, responsible way at a time of real difficulty for this country… I don’t think he’s been at all helpful to the UK national interest, and I think that’s very regrettable indeed.”

Another former British ambassador, requesting anonymity, called him “the least deserving and least qualified foreign secretary of modern times, who has successfully lived down to all expectations”. A senior European diplomat based in London concurred, saying that Johnson was “not taken seriously as a foreign policy actor” and was damaging British interests. He reckoned that three-fifths of the 27 EU ambassadors in London quite like Johnson but consider him ill-suited to the job, while the remaining two-fifths “positively dislike him”.

My interlocutors are, of course, experts in their field and fully paid-up members of the metropolitan elite, so their opinions should be instantly discounted. But forgive me for being perverse. I, too, am dismayed by the harm that Johnson is doing to my country and appalled by the possibility of him becoming prime minister.

Boris Johnson is a singular and unorthodox politician whose electoral appeal transcends traditional party lines. He is charismatic and funny, cultured and erudite, yet blessed with the common touch. He is a wonderful wordsmith, even if he often uses words to deceive and dissemble.

Those talents served him admirably in his role as merrymaker-in-chief while he was mayor of London, but they do not remotely qualify him to govern the UK during a gathering national crisis that he did so much to engender. Nor do I accept the contention that “Boris is Boris” and should therefore be exempted from all the customary rules of personal and political conduct.

Strip away the bluster and bonhomie, and you are left with a chaotic, mendacious, philandering, egotistical, disloyal and thoroughly untrustworthy charlatan driven by ambition and self-interest. Or, as the BBC broadcaster Eddie Mair once put it, “a nasty piece of work”.

Who seriously believes that Johnson gets up each morning and asks himself: “How can I improve the lot of ordinary people?” The notion of him serving the general public, rather than himself, is so manifestly absurd that no answer is required.

***

Contrary to popular perception, Johnson did not enjoy an entirely gilded youth. He was partially deaf until he had grommets inserted in his ears when he was eight. His family moved constantly until his father, Stanley, became one of Britain’s first officials in Brussels, just before Boris’s tenth birthday. His mother, Charlotte, spent many months at Maudsley Hospital in south London with clinical depression. His parents separated when he was 14.

Johnson received a first-class education, however. From Ashdown House Prep School in Sussex, he won a scholarship to Eton where he shone on the rugby field, stage and debating platform. He became head boy before winning another scholarship, this time to Balliol College, Oxford.

In an Eton leaving book, Johnson wrote of his determination to secure “more notches on my phallocratic phallus” – a goal that he amply fulfilled in later life. He then spent a gap year teaching – not “piccaninnies” in some developing country but at Australia’s elite Geelong Grammar School.

At Oxford, Johnson joined the Bullingdon Club, the riotous upper-class dining society, and cultivated the bumbling persona that disguises his political ambition and cunning. He was elected president of the Oxford Union by concealing his Conservative leanings at a time when the centrist Social Democratic Party (SDP) was riding high. He “fully embraced the SDP and the principles and people who supported the SDP to help him get elected,” Frank Luntz, a contemporary who is now a leading American pollster, told Andrew Gimson, Johnson’s biographer. He even denounced Britain’s first-past-the-post system in the union’s presidential debate.

Johnson subsequently explained that his victory required a “deluded collection of stooges” to get the vote out – “deluded” because the victor will not return the favour, so the relationship is “founded on duplicity”. Michael Gove was, by his own admission, one of those stooges. Johnson lacked the application to secure a First, but left Oxford with a fiancée, Allegra Mostyn-Owen, who was reputedly the most beautiful girl in the university. They married in 1987, aged 23. Johnson had to borrow some trousers, having left his behind, and lost his ring within hours.

His first proper job, on the Times, was brief. Asked to write about the discovery of Edward II’s palace, he invented a titillating quotation from his godfather, Colin Lucas, a Balliol history don, suggesting that the king had cavorted there with his catamite, Piers Gaveston. Unfortunately, Gaveston was executed 13 years before the palace was built.

Lucas, furious, complained to the Times. Johnson was sacked. Interviewed by the BBC’s Michael Cockerell in 2013, Johnson said: “It was awful. I remember a deep, deep sense of shame and guilt.” However, it was far from the last time that he played fast and loose with facts – though in his next incarnation, the practice made his name and helped change modern British history.

To sit in the British Library in London, sifting through the articles that Johnson produced as the Daily Telegraph’s Brussels correspondent from 1989 to 1994, was a mildly amusing experience. He revealed European Commission plans to introduce harmonised “Euro-coffins”, ban prawn cocktail crisps and establish a “banana police force”. He wrote stories headlined “Brussels recruits sniffers to ensure that Euro-manure smells the same” and “Threat to British pink sausages”. He reported that Eurocrats had outlawed Italian condoms because they were not precisely 16 centimetres long.

One article announced that sappers were going to blow up the commission’s asbestos-ridden Berlaymont headquarters. Another revealed a proposal to build a “kilometre-high Tower of Babel”, the world’s tallest tower, in Brussels in “the most grandiose scheme ever to cross the desk of an EU official”. A third suggested that Britain would leave the EU and join the European Free Trade Association. That such reports bore scant relation to the truth mattered

little: Johnson’s mission was to debunk the EU at every opportunity.

After his dismissal from the Times, he had been rescued by Max Hastings, the Telegraph’s then editor, who sent him to Brussels at a momentous time in European affairs. Jacques Delors, the commission’s president, was pressing for faster, deeper European integration. Margaret Thatcher was strenuously resisting – or waging “jihad”, as Johnson put it – and had recently declared in Bruges: “We have not successfully rolled back the frontiers of the state in Britain, only to see them reimposed at European level.”

Amid the predominantly Europhile Brussels press corps, Johnson spotted a gap in the market and went for it. In his reportage, Delors was invariably the enemy. British ministers were endlessly ambushed, retreating or isolated as they battled a European superstate whose power emanated “not from the barrel of a gun, but from the Mont Blanc fountain pens of officials”.

“Boris saw Brussels as an easy target. He was not a man who went along with the consensus and was determined to be the grit in the oyster,” George Jones, the Telegraph’s political editor at the time, said. “I think he saw it as a game. It was fun. This was what made politics and reporting interesting.”

But his reporting had far-reaching consequences. It inflamed the smouldering Euroscepticism of the Tory right. Thatcher loved Johnson’s Euro-bashing, allegedly calling him her favourite journalist. So did those cabinet and backbench “bastards” who tormented her successor, John Major. A decade later, Johnson told Sue Lawley on Desert Island Discs: “I was sort of chucking these rocks over the garden wall and I listened to this amazing crash from the greenhouse next door over in England as everything I wrote from Brussels was having this amazing, explosive effect on the Tory party, and it really gave me this, I suppose, rather weird sense of power.”

Johnson also claims credit for persuading Denmark to reject the 1992 Maastricht Treaty, which ushered in economic and monetary union. In a front-page Sunday Telegraph article headlined “Delors plans to rule Europe”, he claimed that Delors wanted to create a permanent “European president” and abolish national vetoes. It was widely reprinted in Denmark before the referendum, the opinion polls turned negative, and the Danes narrowly voted “Nej”.

Charles Grant, the Economist’s correspondent in Brussels at that time who now heads the Centre for European Reform, said that the Danish vote galvanised British Eurosceptics. “It showed they could win,” he told me. “Previously marginal figures like Teddy Taylor and Bill Cash awoke from their slumbers, and from then on British Euroscepticism had a tremendous amount of money and ideas and enthusiasm pumped into it.”

Johnson’s colourful journalism boosted British Euroscepticism in another crucial way. Rival newspapers began to demand the same of their own correspondents, as I discovered when I was posted to Brussels for the Times in 1999. Soon, the notion that Britain was fighting a lone, rearguard action against scheming Continentals bent on destroying our ancient liberties became the only narrative that interested much of Fleet Street. Stories about the EU’s achievements, or the fact that Britain had allies and sometimes won arguments, were seldom printed. In short, Johnson did much to create the crude caricature of Brussels against which he campaigned in the EU referendum a quarter of a century later.

“He set the tone to a large extent for the British media. He had a significant impact,” said the former ambassador Nigel Sheinwald, who was the Foreign Office press secretary in the mid-1990s.

“As a journalist in Brussels, he was one of the greatest exponents of fake journalism,” Chris Patten told me.

“One of the reasons we’re leaving the EU is the media’s insidious drip, drip, drip of anti-EU propaganda over 25 years, which people ended up believing and for which Boris Johnson helped set the tone,” Charles Grant said.

Sonia Purnell was Johnson’s deputy in Brussels and later wrote a biography of him. She saw a side of him seldom apparent to strangers. He was “the most ruthless, ambitious person I have ever met… Under a well-cultivated veneer of disorganisation lay not so much a streak of aspiration as a torrent of almost frightening focus and drive.”

That ambition put paid to his first marriage. He had little time to spare for Allegra, who on occasion had to call the Telegraph in London to find out where he was. Twelve days after they divorced, Johnson married Marina Wheeler, a left-leaning lawyer who was expecting their first child.

Johnson left Brussels in 1994, sped on his way by a pastiche of Hilaire Belloc’s poem “Matilda” composed by James Landale, then the Times EU correspondent and now the BBC’s diplomatic editor. It began: “Boris told such dreadful lies/It made one gasp and stretch one’s eyes…”

***

Johnson returned to London a rising star. He was appointed as the Telegraph’s chief political columnist and began appearing on Have I Got News for You and other television shows. He was put on the Tories’ parliamentary candidates list, despite Major’s protests, and fought the hopeless seat of Clwyd South in the 1997 general election. “I fought Clwyd South and Clwyd South fought back,” he quipped.

In 1999, Conrad Black, the Telegraph’s then proprietor, appointed him as editor of its sister publication, the Spectator. Johnson was a notable success as the magazine’s editor, raising its profile and increasing its circulation.

This was just as well because he sorely tested Black’s patience. He broke his promise not to pursue a parliamentary seat while he was editor by securing the Tory nomination for Henley. Black called Johnson “ineffably duplicitous” but allowed him to remain editor even after he was elected to parliament in 2001.

He had a protracted affair with Petronella Wyatt, a Spectator columnist whom he twice got pregnant. There was no hypocrisy involved because Johnson was not a preachy Conservative who told others how to live. He was, nonetheless, a married man with four young children and brazenly lied when the story broke. “It is an inverted pyramid of piffle,” he declared.

Michael Howard, the Conservative leader, dismissed him as arts spokesman. His wife, Marina, briefly ejected him from the family home in Islington.

Johnson also spread himself thin. As well as editing the Spectator, where his deputy, Stuart Reid, did the hard graft, he was an MP, lothario, television personality, author and columnist on both the Telegraph and GQ magazine, for which he wrote a motoring column. At the Telegraph, he was known as “Bloody Boris” because of his infuriating disregard for deadlines, while several of GQ’s luxury cars ended up festooned with tickets or impounded after he forgot about them.

He earned lavishly – money matters a lot to Johnson – but his parliamentary performance inevitably suffered. His jocular style fell flat in the Commons chamber. He missed many votes. He was a social liberal (given his philandering, he had to be) and favoured small government and lower taxes, but he was driven by no great mission or ideology. He avoided committees and “found parliament a boring, tedious place”, said George Jones, the Telegraph’s former political editor.

David Cameron appointed Johnson, his fellow Old Etonian, as shadow higher education minister after becoming Tory leader in 2005, but he declined to promote him to the shadow cabinet two years later. Johnson had upstaged Cameron’s first conference speech as leader by attacking Jamie Oliver’s campaign for healthier school food. And he had been caught philandering again, this time with a young education reporter called Anna Fazackerley. There may well have been other women. “I haven’t had to have a wank for 20 years,” Johnson is quoted as saying in Gimson’s biography.

Excluded from Cameron’s inner circle, and with Black forced to sell the Spectator by his escalating legal problems, Johnson was tempted to stand for mayor of London in 2008. “I don’t think Boris himself would pretend he had a burning ambition to run London, but what he did have was a burning ambition to get on in politics, and this offered him an alternative route,” Tony Travers, a local government professor at the London School of Economics, told me.

Or, as Gimson succinctly put it: “The role of mayor was Boris’s audition for the top job. His aim was to establish himself as prime minister-in-waiting: the only senior elected Conservative willing and able to stand up to Cameron, and the man to whom the Tories could not help turning when Cameron faltered.”

Lacking another viable candidate and desperate for a high-profile victory to show the Conservatives resurgent after years of New Labour dominance, Cameron reluctantly agreed. With the help of Lynton Crosby, who gagged him, and the London Evening Standard, which shamelessly championed him, Johnson defeated Ken Livingstone in an increasingly Labour-leaning city. He was re-elected four years later (defeating Livingstone again), demonstrating an appeal that stretched far beyond traditional Tory voters.

Johnson’s mayoralty is remembered primarily for his performance as the capital’s cheerleader during the 2012 Olympics. The role was tailor-made for his ebullient personality, especially in the jittery prelude to the Games. Even when he got stuck on a zip wire – a mishap that would have sunk most conventional politicians – he used humour to turn it to his advantage.

***

The Olympics apart, Johnson’s record was not stellar. Unlike Livingstone, who brought in the congestion charge, he took no particularly brave or contentious decisions. He encouraged cycling and introduced “Boris Bikes” – an idea first mooted by Livingstone – but at huge expense. He replaced Livingstone’s reviled bendy buses with stylish but very costly new Routemasters. “Vanity projects” such as the ArcelorMittal Orbit tower and the Thames cable car have hardly been popular. His Garden Bridge project has been scrapped. He fought in vain for a new London airport in the Thames Estuary.

Johnson’s greatest test was the London riots of 2011. He was found wanting. He took three days to return from holiday in Canada. He misjudged the mood when he did and was jeered by victims. Later, he bought three second-hand German water cannon, only for Theresa May, then home secretary, to ban their use.

He continued to write his Telegraph column while mayor, adding £250,000 to his official salary of £140,000, but reneged on a promise to give a fifth of his journalistic earnings to good causes.

There was also, inevitably, another sex scandal, despite the advice that Max Hastings gave “Bonking Boris” when he was contemplating a mayoral bid: “Lock up your willy.” Helen Macintyre, an art dealer, had a daughter by him. Macintyre’s partner, Pierre Rolin, who had given Johnson an £80,000 donation, protested: “He has no moral compass whatsoever.” Johnson was again ejected from the family home.

A close associate of Johnson during his mayoralty told me that he was a brilliant public performer but an “absolutely terrible manager” who was saved by his chiefs of staff, Simon Milton and Edward Lister. He had a short attention span and a weakness for “headline-grabbing projects”. He loved to be loved and found it so hard to say “no” that aides never allowed him to meet Bob Crow, the transport workers’ leader, lest he gave away the store.

Travers argues that Johnson was “not a bad mayor” but was exceptionally lucky: to run against Livingstone when Gordon Brown’s Labour Party was collapsing; to inherit a dynamic and growing capital; to have government money pumped into London ahead of the Olympics; to have no terrorist attacks on his watch; to take office with such low expectations. “The very least you can say of Boris Johnson’s tenure is the city didn’t get worse, and certainly transport got better.”

But Johnson’s mayoralty served his political purposes admirably. It kept him in the spotlight, negated the charge that he had never run anything and enabled him to carve out a distinctive platform for the day that David Cameron left office.

Ever disloyal, he regularly took issue with the prime minister and the chancellor, George Osborne, who was at that time his strongest rival. He opposed Cameron’s contention that Britain was broken, reductions in police numbers, the 50p tax rate, housing benefit cuts and “any kind of Kosovo-style social cleansing in London”.

By the time Johnson’s second term ended, in May 2016, he had returned to parliament as MP for Uxbridge and South Ruislip and was Britain’s most popular politician. That is why his decision to campaign for Brexit was so crucial. He gave the Leave camp a glamour and heft that it would never have had were Nigel Farage or Iain Duncan Smith its figurehead.

***

I don’t know why Johnson backed Leave, but there’s ample circumstantial evidence to support the charge that he did so for political advantage: win or lose, he would put himself in pole position to lead a predominantly Eurosceptic Tory party after Cameron’s departure. I haven’t spoken to anybody who doesn’t say that Johnson is kinder about the EU in private than in public. He was raised in Brussels, the son of a Eurocrat-turned-MEP, speaks French and Italian and takes holidays on the continent. He backed Ken Clarke, the Tories’s leading Europhile, for party leader in 2001. For eight years, he led the world’s most cosmopolitan city – one that depends on international finance and immigrant labour. He even proposed an amnesty for illegal immigrants. “A lot of the things he argued for as mayor of London seem now to be stuffed in the broom cupboard,” Chris Patten noted.

That he drafted two Telegraph articles – one making the case for leaving the EU and the other for remaining – also suggests that his decision was based more on political expediency than deep conviction. “I’m very cynical about Boris. I don’t believe he believes in anything apart from himself and his own ambition,” I was told by someone who had known him for many years.

What is indisputable is that Johnson proceeded to spearhead a shamefully mendacious campaign. There was the spurious “Brexit bonanza” of “£350m a week” – a promise plastered over his campaign bus; the preposterous claim that Turkey was about to join the EU, unleashing a tsunami of 80 million Muslims on the UK; the failure to acknowledge that immigrant workers, far from overloading the NHS and other public services, actually keep them afloat; the peddling of phoney patriotism and the dangerous illusion that Britain can go it alone in a globalised world; the likening of the European Commission to Hitler’s Third Reich; and those blithe assurances that divorce from the EU would be simple and painless because Germany is desperate to sell us cars. Johnson quipped, “My policy on cake is pro-having it and pro-eating it” – surely one of the most irresponsible sentences uttered by any politician.

Nobody seriously suggests that Theresa May subsequently made Johnson Foreign Secretary because he was the best man for the job – he had no ministerial experience and had managed to insult half the world’s leaders in his columns. She did so primarily because she had to give a top job to a leading “Leaver”, and she intensely disliked the other contender, Michael Gove.

As Foreign Secretary, Johnson has continued to undermine Britain’s interests by going around the world giving needless offence. At an early reception, he greeted foreign ambassadors by declaring: “We have invaded, defeated or conquered most of your countries, but we are here as friends.” Arab and African ambassadors considered it a “ghastly joke”, a source told me.

He compared François Hollande, the former French president, to a Nazi prison camp guard determined to punish anyone trying to escape from the EU. He caused anger at the Munich security conference by talking of Britain’s “liberation” from Europe. He was rebuked by Downing Street for (rightly) accusing Saudi Arabia, a major trading partner, of waging “proxy wars” in the Middle East. He cited Rudyard Kipling’s colonial lament “The Road to Mandalay” in Myanmar. He asserted that Libya’s war-torn city of Sirte could become a new Dubai if they “clear the dead bodies away”.

Having demanded during the EU referendum that David Cameron should pledge to veto Turkish membership of the EU, he enraged Britain’s European partners by promising to help Turkey’s bid “in any way possible”. He further antagonised them by suggesting that they “snapped out” of their “collective whingerama” following Donald Trump’s election victory. He told them to “go whistle” for any British divorce payment.

“He seems unable to pursue a serious argument without resorting to mop-headed witticisms,” Patten said. Johnson is now “toxic” to most EU politicians, Charles Grant added. He and the Prime Minister have few European allies left, and: “We’re not going to get a half-decent Brexit deal without a lot of goodwill.”

But the criticism goes beyond Johnson’s gaffes. Former diplomats accuse him of lacking an overarching foreign policy (he has given only two or three set-piece speeches in 16 months) and going largely AWOL on the major issues of the day – Syria, North Korea, Russian aggression and Trump’s destabilisation of the established order.

Johnson did seek to persuade the G20 to sanction Russia after a chemical weapons attack by its Syrian regime allies last spring, but he was humiliatingly rebuffed. In another sign of Britain’s diminished influence, the UN general assembly voted overwhelmingly in June to refer a dispute over the Chagos Islands to the International Court of Justice, with most EU states declining to back Britain. “Foreign secretaries used to cut ice abroad,” Lord Kerr of Kinlochard, a former ambassador to the US and EU, recently lamented in the London Evening Standard. “Everything is a bit slapdash, seat-of-the-pants stuff,” said another diplomatic source.

The Foreign Office is not responsible for the single biggest challenge currently facing Britain – negotiating Brexit. But Johnson’s critics are still scathing about his failure to lubricate those negotiations through quiet diplomacy, or to develop a realistic vision of Britain’s post-Brexit role. They accuse him of undermining the Prime Minister’s negotiating hand by issuing personal red lines designed primarily to boost his standing with Tory anti-EU zealots.

Senior European diplomats agree. He has no plan, vision or strategy for Brexit, one told me. He is guilty of “magic thinking – thinking it will be wonderful and therefore it will be.”

My requests for an interview with Johnson went unanswered, but he does have defenders. They say that he travels prodigiously and works very hard, rising at 5am to go through his red box and sometimes calling his officials late in the evening. Those officials are said to like him personally and enjoy his company. He can charm as well as offend foreign dignitaries, and he happily chats to junior Foreign Office staff while queueing for lunch in the canteen. Asked to name Johnson’s biggest achievement, one source said that he had “put some adrenalin back in the Foreign Office” after Philip Hammond’s tenure.

Johnson’s defenders also argue that he is in an impossible position: if he makes high-profile appearances, or boasts of his accomplishments, or calls for a “global Britain”, he is accused of “going on manoeuvres” – seeking May’s job. They say that he attracts headlines in a way that no other politician does, and often unfairly: the Kipling poem he quoted in Myanmar had apparently been cited by Aung San Suu Kyi at a dinner the previous night.

Nonetheless, even his ministerial team at the Foreign Office is said to be unhappy. The intelligence services are believed to be wary of sharing sensitive information with him, and on occasion relations with his instinctively Europhile civil servants have been strained. “There are moments when he says, ‘Come on, we’ve got to make this work. Stop being gloom-mongers,’” one source said.

Nobody could accuse Johnson of gloom-mongering. “Let the British lion roar,” he proclaimed in a speech to last month’s Tory party conference that was calculated – not for the first time – to evoke comparisons between him and Churchill, about whom he wrote a book. The former diplomats scoffed. “Churchill would have thought he was a second-rate chancer,” said one.

***

Could Boris Johnson really succeed Theresa May as prime minister? He is the bookmakers’ favourite and still loved by much of the ageing, shrinking party membership that makes the final choice. The crucial question is whether he would be one of the two candidates the party’s 316 MPs submit to those 100,000-odd members.

Johnson was never popular within the parliamentary party. He was not “clubbable”. He did not frequent Westminster’s tearooms. He represented no particular strand of Tory ideology, and if the concept of “Johnsonism” existed at all, it was widely seen as the promotion of himself. Nor, beyond winning London twice, did he have any great political accomplishments to his name. “He’s spectacularly ambitious without much of a record to justify that ambition,” said Chris Patten.

He is even more unpopular with his fellow MPs today, having enraged them with his disruptive, self-serving, headline-grabbing challenges to May’s authority before last month’s party conference. He has no obvious allies left at the top of the party. “Who in the cabinet would trust Boris? I can’t think of anybody,” a leading political journalist said.

George Osborne, who now edits the London Evening Standard and retains some influence among Tory MPs, “would do anything to stop Boris”, a well-placed source told me. One senior Tory MP – no friend of Johnson – put his core support at just 15 MPs, saying: “Over the past six months, he has totally eroded his own base by rendering himself less and less substantial and responsible.”

Indeed, I was struck while researching this article that the more dealings people had with Johnson, the less most seem to like or trust him – witness Michael Gove by the end of the referendum campaign. “He’s someone towards whom your feelings don’t become warmer the more you know him because he can’t resist shafting people. He’s so selfish and so ambitious, he’ll do the dirty on anyone impeding him from doing what he wants,” said someone who has known him for many years.

Ultimately, Tory MPs might still back Johnson if they consider him the candidate most capable of defeating Jeremy Corbyn in a general election. But it is no longer obvious that he is still the “Heineken Tory” who can attract parts of the electorate that no other Conservatives can reach.

Brexit was the first truly divisive issue on which Johnson had ever had to take a stand, and it has hurt him. He was jeered by irate Remainers as he left his Islington home the morning after the referendum. At June’s general election, his majority halved in Uxbridge. A solitary YouGov survey in September gave him a net favourability rating of minus 19 per cent. Even within the Johnson family, there has been unrest: his sister, Rachel, has joined the Liberal Democrats.

Nowadays he makes few public appearances beyond the morning runs that he takes from his official residence at Carlton Gardens, where he stays most nights rather than returning home. That is partly the nature of his job, but it might also be that he fears the reception he would receive. “Deep down, he struggles with what’s happened since the referendum and why so many people hate him,” said another source who knows him well.

Arguably the Conservatives’ biggest potential vote winner is not Boris Johnson but Ruth Davidson, who has revived the Scottish party. “The crown has been handed on. She’s the bright young thing in the party now,” one observer of the Tories told me. “Boris is last year’s model. His time is past.”

Davidson has also made fewer enemies than Johnson, and that matters. Nick Robinson, the BBC’s political guru, told me that his “law of leadership elections” runs thus: “If anybody would die happy if their final act is to stop you reaching the top, you won’t reach the top.” He added: “I’d use Michael Heseltine, Michael Portillo, Ken Clarke and Ann Widdecombe as illustrations, and my instinct is that Boris now falls in that category.”