It is fair to say that the prospect of Boris Johnson becoming the next prime minister of Great Britain and Northern Ireland has not been universally welcomed on this side of the Atlantic.

The 55-year-old Conservative member of Parliament is often described as a “Marmite figure”, a reference to a salty, waxlike substance that some British people like to spread on their toast. You either love Marmite or you hate it, and the same goes for Johnson. About half the nation breaks into a smile whenever the bumbling, self-deprecating, overgrown schoolboy heaves into view. The other half breaks out in hives.

Having known Boris since 1983, when we were at Oxford together, I am a fan. He has been described as looking like a sheepdog peeping out from under an upturned colander of spaghetti — he has a thick mop of blond hair that Donald Trump would kill for — and that was as true then as it is today.

The striking thing about him as a 19-year-old student is that he was already the finished article, whereas the rest of us were still works in progress. It is not just that he was comfortable in his own skin. He had a Churchillian sense of his own destiny. He gave the impression that at some point in Britain’s future, at a time of national crisis, he would sweep in and save the day. We are about to find out if that was a narcissistic self-delusion or an historical premonition.

First, the case for the prosecution. Before entering politics, he had a successful career as a journalist — he became the editor-in-chief of the Spectator, a prestigious conservative weekly, at age 35 — but was fired from his first job, at The Times of London, for inventing a quote and attributing it to his godfather.

His reputation for being less than honest followed him into politics. As the Conservatives’ shadow arts minister in 2004, he assured Michael Howard, the leader of the party at the time, that rumours of his adulterous affair with Petronella Wyatt, the Spectator’s deputy editor, were “an inverted pyramid of piffle”. When they turned out to be true, Howard sacked him.

The highest office he has occupied was secretary of state for foreign and commonwealth affairs from 2016 to 2018, and he did not cover himself in glory. Until that point, people assumed his befuddled persona was just an act, but he was not always on top of his brief as foreign secretary, such as the time he told Parliament that a British woman, Nazanin Zaghari-Ratcliffe, who had been arrested in Iran, had been “simply teaching people journalism”. That did not reassure the Iranian authorities, and she remains in prison to this day.

What can be said in Johnson’s defence? Well, his journalism may occasionally stretch credulity, but he is one of the funniest writers — and speechmakers — of his generation. He is also marvellously politically incorrect, the real reason he is so widely disliked by Britain’s sanctimonious Establishment. In a column for The Daily Telegraph last year, he compared burka-wearing Muslim women to “bank robbers” and “letterboxes” jokes that led to accusations of “Islamophobia” even though he went on to oppose Denmark’s burka ban in the same column.

An army of offence archaeologists has trawled through everything Johnson has ever said or written, frantically searching for evidence of his “bigotry”. But the truth is he is a liberal conservative who is pro-immigration and once joined a Pride march wearing a pink cowboy hat.

Yes, he was an underwhelming foreign secretary, but he enjoyed huge success as Mayor of London, first beating the hard-left incumbent, Ken Livingstone, in 2008 in what has traditionally been a Labour-supporting city, and then winning reelection. During Johnson’s eight years in office, crime plummeted, construction boomed and he cut road traffic fatalities by 50 per cent. He went on to shore up his bona fides as an election-winning machine when he led the “Leave” campaign to victory in the 2016 European Union referendum.

And it is this, above all, that makes him the ideal successor to Theresa May as prime minister. Johnson has pledged to take Britain out of the EU by October 31, deal or no deal, and if he pulls that off, he will likely have no problem winning a General Election.

But what if Parliament obstructs him, as seems likely? In that scenario, he will almost certainly have to fight an election in much more precarious circumstances, facing the anti-EU Brexit Party on one side and a Labour Party led by Jeremy Corbyn on the other.

Corbyn is a capitalism-hating socialist of the old school, who, until fairly recently, hailed Hugo Chávez’s leadership of Venezuela as a blueprint for Britain. If there is an election before Britain leaves the EU, Boris Johnson looks like the only Tory who can beat Corbyn and avert that catastrophe.

Will Mr Marmite prove to be Britain’s Mr Incredible? Many people do not think so, but I would not bet against him.

• Toby Young is a columnist for the Spectator