Video report by ITV New Political Correspondent Libby Wiener
Profile by ITV News Multimedia Producer Narbeh Minassian
ITV News speaks to people who've worked for Boris Johnson, met him on the campaign trail or studied his life to get a new view on the new PM.
It was little more than a year into Boris Johnson’s time as Mayor of London, his first truly major role in the public spotlight since becoming an MP in 2001.
Mr Johnson - full name Alexander Boris de Pfeffel Johnson - was in Lewisham, south-east London, in June 2009 for a relatively routine photo opportunity rummaging for rubbish in a river.
It was never expected to make headlines in the national press but, as has been the case for most of his life, the norms don’t always seem to apply to the old Etonian.
Taking careful steps in the shallows with high boots on, he slowly ambled forward and found himself in full view of the press.
One more step and Mr Johnson was suddenly sinking and had to be helped out of the water.
It was a classic gaffe that made headlines everywhere – but was it really a mistake?
“I've never been convinced that that was an accident,” Jo Tanner told ITV News.
The PR expert, who headed up communications for Mr Johnson's successful 2008 mayoral campaign, said the river plunge had all the hallmarks of a natural born self-publicist.
“This was a man who knew that some of these events were probably quite dull and actually he used his own charm and wit and ability to get attention to ensure that they were covered,” she said.
“I think it was more about making sure that got some attention,” she said.
If anyone didn’t know Mr Johnson before he was mayor, they certainly knew him then.
And now, almost exactly a decade later, Mr Johnson is getting ready to move into Downing Street.
Mr Johnson's biographer Andrew Gimson poured over every element of this singular politician's life for his book Boris: The Rise of Boris Johnson, released in 2006.
He told ITV News a characteristic he found that has run through the new PM's life was an inability to conform to - if not entirely disregard - the rules.
“We do have an unwritten constitution… I don’t think he will be unconstitutional," Mr Gimson said, while giving his thoughts on how Mr Johnson would play his hand in Europe.
"But I think he will sometimes insist on doing things his own way.”
This apparent disregard for protocol was noted at Eton College when the 18-year-old pupil's teacher Martin Hammond warned his family about an apparent sense of self-entitlement.
“Boris really has adopted a disgracefully cavalier attitude to his classical studies,” he wrote to Mr Johnson's father Stanley Johnson in April 1982.
“Boris sometimes seems affronted when criticised for what amounts to a gross failure of responsibility (and surprised at the same time that he was not appointed Captain of the School for next half).
“I think he honestly believes that it is churlish of us not to regard him as an exception, one who should be free of the network of obligation which binds everyone else.”
Despite this apparently brash and individualistic approach, Mr Johnson hasn’t been one to shun company or beneficial support.
Mr Gimson told ITV News: “I have observed that throughout his life he has been very good at enlisting the help of people who somehow find themselves looking after him.
“I’m not saying (Mr Johnson's girlfriend) Carrie Symonds will play that role, but he will palpably need someone to make sure that he’s got a sort of, you know, pair of socks or something to put on in the morning.
“He will find people who somehow find it quite amusing to help him stay on the road.”
But the MP for Uxbridge and South Ruislip has always been able to find a connection with people, Mr Gimson said, and has “an astonishing link with the wider public”.
“He can go into a very dull shopping centre on a Wednesday afternoon and change the atmosphere, which is an unusual thing,” he said.
And that’s exactly what happened with 24-year-old Daniel Jones, who met Mr Johnson outside a shopping centre in Uxbridge in his teenage years.
“I met him when he was running for Mayor of London,” he told ITV News, while sitting with two friends at a pub on Uxbridge High Street.
“I was 14 and skateboarding when some old people had a go at me for skateboarding near a shopping centre with a hoodie on.
“Then Boris had a go at them for having a go at me and he stopped me to speak. He suggested I pick up the skateboard and walk, the last thing he said to me was ‘make sure your parents vote for me’.”
Mr Jones, along with 24-year-old friends Matt Corker and Mark Windle, agreed they would be happy to have Mr Johnson sit down for a drink with them.
The same could not be said by a Tory party member of more than 50 years, who met Mr Johnson a few years ago and dismissed him as a “model for everything a politician shouldn’t be” while testifying to his success meeting voters.
Unwilling to give his name for fear of expulsion, he told ITV News he once accompanied Mr Johnson to a pub in Uxbridge and witnessed his “magnetic personality”.
“If I walk down a road with him, he is surrounded by people, often with youngsters wanting selfies,” he said.
“He is a master of self-publicity. When we went to the pub he ended up with his picture behind the bar with him pulling a pint.”
But the Tory member added Mr Johnson “does not know when to keep his mouth shut” and “has a knack of opening his mouth and putting his foot in it”.
With his head in his hands, he referred to the case of Nazanin Zaghari-Ratcliffe and labelled Mr Johnson’s handling of that issue as Foreign Secretary “appalling”.
“And where does he get his shirts from?” He said.
“I have always wondered how someone who was a member of the (Oxford University) Bullingdon Club could have his shirt hanging out the back.”
Many of the residents in Uxbridge who spoke to ITV News said they had not met their MP but - like most of the rest of the country - formed their impressions of the new PM from his role in public life and the media.
Seventy-year-old Sue Curtis said: “Just going off what I see on the telly and he’s a likeable fella, he might not be very good at running the country but is he going to be any worse than Theresa May?”
It remains to be seen if Mr Johnson will soon find himself out of his depth or can make a notable splash in power - just like that summer’s day in the rubbish-strewn Lewisham river 10 years ago.
Mr Gimson reckons people “wearily” putting the TV on at the end of the day might actually enjoy a PM who is prone to a pratfall.
Recalling Mr Johnson's most famous gaffe when he got stuck on a zipwire holding two union flags in 2012, he said: “He likes being spontaneous and, as that zipwire showed, unlike most Englishmen he doesn’t mind making a complete bloody idiot of himself and I’m sure he will sometimes.
“And the press will say ‘ooh what a terrible gaffe’ but it won’t necessarily be to his disadvantage.”
Mr Johnson's former campaign PR manager Ms Tanner however said those expecting a buffooning prime minister may be surprised.
She told ITV News those who know Mr Johnson personally realise he has become a “much more serious character” for some time.
And with that she thinks he may call time on his proven PR strategy.
“It's very clear that as prime minister there are lots of important issues that are going to be going on. Everything you do is going to be watched by the media," she said.
"I don't think there is going to be the need to draw attention to things in perhaps the same way he might have wished to before.”