Boris Johnson's first frontbench job for the Conservative Party came 15 years ago, when leader Michael Howard appointed him shadow arts minister on May 7, in the spring of 2004.

Somehow, there was a mixup. News of the promotion was broken to Johnson not by his leader, but by the Daily Telegraph's political correspondent, Toby Helm.

"After recovering from the surprise," Helm wrote of Johnson's characteristically dishevelled reaction, "he described it as 'a great honour', adding: 'Look the point is … Er, what is the point? It is a tough job but somebody has got to do it'."

Johnson also mentioned that he knew an "awful lot" about the arts, having studied painting and drawing at his prep school — a claim on which the newspaper tested him the following day by asking him to complete a 20-question quiz.

It didn't go well.

DT: Name the young actor now playing Hamlet at the Old Vic.

BJ: That is so obvious! It's, oh God … hey. Is it the Old Vic? Now, let me just think … would it be … I know what. Is it the son of Timothy West? I know everybody is talking about it. It's my wedding anniversary tomorrow and we'll go to see it at once.

By question six, the cold fingers of panic were taking hold.

DT: Who was recently appointed artistic director of the Old Vic?

BJ: Um … Trevor Nunn? No, no, Jesus Christ, Nicholas Hytner. Oh, God. I don't know. Basil Brush! This is not fair. I don't know anything about the contemporary arts scene.

DT: Name the male Turner-Prize winner who wears frocks.

BJ: This is hopeless. I want to give up. Why can't you ask me about the proper arts? You know, poetry and literature. These questions are all about what luvvy does what.

Each British Prime Minister must seek the approval of their sovereign in order to form Government. ( AP: Victoria Jones, pool )

By question 10, a surly mood had ensnarled the subject.

DT: Who designed the sun at Tate Modern?

BJ: Who designed the what? You mean that glowing thing? Well, the original design was by God. This was an imitation. It was wholly derivative. Who's it by? I don't know. Jay Jopling. I don't give a monkey's.

So began Alexander Boris De Pfeffel Johnson's executive career in the Conservative Party. This first stint wasn't to last long. By Christmas 2004, he'd been sacked by Howard for shagging one of his columnists at The Spectator — a political magazine of which, consistent with the baffling British practice of not minding even the most egregious conflicts of interest, he had remained editor throughout his term — and then denying to his leader that he'd done any such thing.

(Of the interference between the two roles, he would later acknowledge: "I have successfully ridden two horses for quite a long time. But I have to admit there have been moments when the distance between the two horses has grown terrifyingly wide, and I did momentarily come off.")

But in that first interview as the alternative British minister for the arts, Boris Johnson pioneered something: creative incompetence as a political device.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 22 seconds 1 m 22 s Mr Johnson spoke of "energising" the United Kingdom in a speech after the outcome of the vote was announced.

The rough alchemy of politics had heretofore been fairly consistent; if you're asking for a job, at least make some show of knowing what you're talking about.

And it would be another 12 years before Donald Trump (who in 2004, as Boris Johnson flubbed the Telegraph's arts quiz, was shooting his first series of The Apprentice, a TV show from which Trump estimates he made a quarter of a billion dollars) won the White House with an unnervingly similar formula: unrepentant concupiscence, failure to tick conventional expertise boxes, and a distinct fluidity of personal allegiance.

In the US, Trump identified as a Democrat for much of the century's first decade. And in the UK, before he shocked his prime minister and university drinking club compatriot David Cameron in 2016 by coming out as a pro-Brexit campaigner, Boris Johnson drafted three columns on the subject for the Daily Telegraph; two that argued for Brexit, and one against. The latter was not published until discovered much later by a rival paper.

Bob Woodward's book Fear: Trump In The White House portrays a President so far adrift from the conventional competencies of public administration that he's essentially in his own stratosphere. In Michael Lewis's transfixing The Fifth Risk, the author describes what happens to whole government departments when an incoming President simply does not recognise or care about the work they do.

But the American people elected Trump; actively chose him over the homework-doing Hillary Clinton.

The US President claimed Johnson's ascension to the leadership as a personal vindication. "He's tough and he's smart. They're saying Britain Trump. They call him Britain Trump … they like me over there. That's what they wanted. That's what they need. He'll get it done. Boris is good. He's gonna do a good job."

There are deep differences, obviously, between the two men, but they share something remarkable.

Each has managed to construct his own one-man political microclimate, in which deeds or omissions that would historically be career-ending for a national leader are somehow accepted as part of the spectacle.

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'Crazed wasps in a jam jar'

Trump's weapons-grade solipsism is different from Johnson's style of radical self-effacement ("All politicians in the end are like crazed wasps in a jam jar, each individually convinced that they are going to make it," he told Desert Island Discs in 2005, admitting that he still harboured dreams of the prime ministership), but in the end they both back their own ability to defy conventional orthodoxy, and respond to any situation fluidly based on the most urgent need of the moment.

When Tony Abbott first visited the UK as Australian prime minister in 2013, a meeting with Johnson — then mayor of London — was arranged. Bounding forth to meet Abbott, Johnson extended jovial greetings, adding: "Now, would it be more helpful to you if I endorse you or denounce you?"

Later that year, Johnson came to Australia to speak at the Melbourne Writers Festival. I flew to Melbourne to interview him at a festival event.

Johnson was late, and when he appeared (the session was at about midday) it became apparent very quickly that he was suffering the after-effects of the significant amounts of red wine he'd consumed the night before. I say it "became apparent", but essentially he announced this detail upon entering the room.

In the minutes available for conversation before the event, his most significant worry was not that he'd say something rash, or throw up into a pot plant, but that he would be dull. And at the very end of our hour on stage, this still seemed to be a concern for him.

The time was up, but I judged there was room for one more, very brief question. A bloke up the back asked Johnson if there was still a place for the classics in modern education.

Oh indeed, Johnson replied. If for no other reason that an Australian student — if ever trapped up a mangrove with an angry crocodile at the foot — could do what he himself did in times of trouble, and keep himself conscious by reciting all the poetry he had at hand.

And then he began to recite The Iliad. In the original Greek. Minute after minute passed, as Johnson held forth and gesticulated, sometimes rising from his chair to emphasise a powerful line. The longer it went, the more the audience loved it.

Watch Duration: 3 minutes 39 seconds 3 m 39 s Watch Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Boris Johnson recites extracts of "The Iliad" in Greek

An insight into how Boris works

The British journalist Jeremy Vine tells an anecdote about Johnson that is, while essentially trivial, a spectacular insight into the man's modus operandi.

Vine is scheduled to hand out awards at an event for the securitisation industry at which Johnson is the keynote speaker.

Johnson shows up one minute before he's due to speak, and appears to know neither a) that he's supposed to be speaking nor b) what securitisation is.

At this point, Vine (who has prepared with average diligence for the event) is paralysed with horror, but realises — as Johnson bumbles up on stage, overtly checks the banner behind him for the name of the organisation, gabbles something about sheep, then tells a completely irrelevant joke to which he forgets the punchline — that he's in the presence of greatness.

The audience loves it. And the whole thing becomes a great dinner party anecdote for Vine until, 18 months later, the journalist finds himself at another awards night for another unmemorable industry group at which Johnson is the featured speaker.

Again, Johnson crashes in with minutes to spare. And as Vine watches, utterly flummoxed again, but for different reasons, Johnson completes the same routine. Same sheep story, same ostentatious glance behind him to check the name of the awards, same joke, same forgotten punchline.

The power of incompetence may be one of the most inscrutable phenomena of the modern political age, but it certainly works.

Why else would a man like Boris Johnson feign it so carefully?