LONDON (Reuters) - In the evening sun near Tower Bridge, people watch Olympians on a big screen and cheer. High above them, on the top floor of the bulbous glass building where he has his office, Mayor of London Boris Johnson is addressing technology entrepreneurs in a speech that underlines his ideology.
Why does Usain Bolt run fast, he asks. Competition - that's why.
The excitement of the crowd outside penetrates the open windows. The blond mop-haired mayor, selling the British capital in a reception in the penthouse, warms to his theme. Another example comes from science.
The 17th-century scientist Robert Hooke, Johnson notes, was also competing fiercely with others in London when he worked out the law of elasticity.
Strain is equal to stress - "as I proved on that zip wire the other day".
The reference - to the minutes when the Mayor of London dangled helplessly from an aerial runway above the assembled crowd in a park - raises a laugh. "Ut tensio sic vis," booms Johnson, offering Hooke's Law in Latin. The audience roars.
Boris Johnson, or plain "Boris" as he is known to most British people, was the political victor at the London Olympics. From the 48-year-old's plummy tones encouraging Underground commuters to avoid congested stations to his imitation of Bolt's victory pose, or his prose likening female beach volleyball players to "glistening otters", he turned 2012 into Boris's Games.
Some say he is an unashamed self-publicist seeking political advantage, some an eccentric, enthusiastic mayor promoting his city. But many pundits believe he ultimately wants the top job.
Britain's current prime minister, David Cameron, went to Eton, the elite fee-paying school, just like Johnson, and shared his Conservative beginnings at Oxford University. Cameron said Johnson "defies all forms of gravity" and called him a "titan" of their Conservative Party.
In the real world, the economy is struggling, Johnson's critics are angry that his warnings on the Underground put people off visiting London, and Britons are asking whether the Games have been worth the 9-10 billion pounds investment.
But inside the Games bubble, Johnson, a free-market defender of the banking classes, has repeated a relentlessly upbeat story that attracts the most incongruous support. "I'm incredibly left-wing and I absolutely love Boris Johnson," said Lucy Lapham, a 27-year-old event manager.
"He's come down to our level almost," agreed her friend, Victoria Stickland, 24.
For Alexander Boris de Pfeffel Johnson, who was born in New York General Hospital in June 1964, the London Games kicked off with a trim of the unruly blond hair that gets mussed up on camera, and a promise that the "Geiger-counter of Olympomania" was headed "Zoink!" off the scale.
Handing financial decision-making for London over to local council officers for the duration of the Games, he took to the stage in Hyde Park.
There he promised the crowd "more gold, silver, bronze medals than it takes to bail out Greece and Spain together".
By the opening ceremony, Georgina Wharton, a 30-year old from Melbourne, Australia, said the best thing about Boris was that he is immune to the political correctness she sees everywhere in Britain.
"He just doesn't care," she said admiringly.
On day one of the Games, Johnson was on camera with Queen Elizabeth, complimenting her for her performance with James Bond in the "magnificent and bonkers" opening ceremony.
By day three, there were headlines about empty seats at Olympic venues. Businesses were blaming his warnings for a slump in their trade. Johnson schmoozed representatives from the creative industries to encourage them to invest in London. He and his staff would, he vowed, "kick down the doors" for them.
By the end of the Games, Johnson's exaggerated claims about the benefits of investing in London had peaked: "Put simply," he said, "there is no other place on the planet where investors will see greater returns."
Those who know Johnson say that, beneath the cultivated buffoonery, he is an intelligent, serious politician.
His slapstick moments - including a tumble into a river in east London in 2009 - combine with enthusiasm for the eccentric genius of Britain. A journalist as well as a politician, the twice-married Johnson relies on humour and charm to divert attention from a history of sexual affairs.
He has a deft touch with what he calls the "blessed sponge of amnesia", ensuring that he claims credit while others shoulder blame. When he was first elected mayor in 2008, he won more than a million votes - the largest personal mandate of any politician in British history.
The Conservative Party has not won an absolute parliamentary majority for 20 years, and now some of its members and even some polls suggest he could lead the country, although Johnson says this is nonsense. "How could anybody elect a prat (fool) who gets stuck in a zip wire?" he said.
"I think people will look back on these Olympics as a time of great pride," said Tim Montgomerie, editor of a website for Conservative activists. "The whole thing has been magical, and he just seems to have captured the mood."
For Montgomerie, comparisons between Johnson and wartime leader Winston Churchill are not out of place. Like Churchill, he said, "Boris has all kinds of character question-marks about his suitability for the top job, but there is a precedent there, someone who worked out incredibly well".
Many of the London businesses that hoped for a boost from the Games would disagree. Johnson's transport warnings were stopped, but too late for them. Near Olympic venues, the sheer volume of people have prompted crowd-control measures that have hurt business, they say.
At a souvenir stall outside Hyde Park, where live screens have broadcast the Games to thousands of spectators, business has been only OK, says the stallholder: "When it gets too busy we have to shut," she said. "That's one of the things they don't tell you beforehand."
In London's Covent Garden piazza, a year-round tourist hub in the theatre district, Benjamin Pollock's Toyshop did not see the summer crowds who buy its eccentric stock of finger puppets, jumping jacks, antique toy theatres and other trinkets for children.
"It's been a bit of a disaster," said part-owner Louise Heard, laughing. She wants the mayor to help.
"He's the face of London, isn't he? If Boris came out and said tomorrow, 'You know, the Olympics is great, but hey everyone, go shopping' ... if he's seen falling off a zip wire, then he can come do a stunt in the centre of London perhaps."
To some extent, the mayor's high-wire act distracted the media from less positive stories, including the fact he had invited media baron Rupert Murdoch to an Olympic swimming event.
That day Johnson also gave an interview to Murdoch's Fox News. "It's all going horribly right - touch wood," he said.
The invitation to Murdoch, whose titles are under investigation for alleged phone-hacking by staff, angered Johnson's opponents. Murdoch titles including the Sun have for years been able to make or break political careers in Britain, a fact underlined by the phone-hacking scandal.
As mayor, Johnson is in charge of the police who are conducting the probe into phone-hacking. His opponents were angry. "The mayor is acting in his own interests and not those of Londoners," said Liberal Democrat Stephen Knight.
Where in the old days Cameron would ask Murdoch to use the back door on his visits to Number 10 Downing Street, Johnson was photographed at the Olympic Aquatics Centre with Murdoch, and said the 81-year-old was one of 23 executives he had hosted.
Murdoch's Sunday Times followed the Sun this week with a positive opinion poll about the mayor. It found Johnson would be the preferred choice for 24 percent of voters to become Conservative leader if Cameron stepped down. Other surveys have underlined the point.
In Hyde Park, though, Games spectators were more cautious. Londoners Yasmin and Fadumo, 16, for example. Sitting on the ground watching the screens, they say the Games have been "really great". But they do not know Boris Johnson.
Leon Oliver, 19, wearing union flag tights, hat and jacket and his face painted with a union flag, certainly knows the London mayor and has enjoyed his antics immensely.
"I wouldn't put him in charge of the country," said the student from Bristol. "Within Britain we have our own humour. Everyone finds him hilarious, but I don't think the world would find him hilarious. I think they'd think he was a bit of a prat." (Additional reporting by Karolin Schaps and Sophie Kirby)