Anthony Joshua used to run a stall at Wembley market that sold what his promoter Eddie Hearn has called “dodgy belts”. Heavyweight boxing, the sport in which Joshua has made a name and a great deal of money, has long had a problem with dodgy belts.

There are currently no fewer than six world heavyweight belts, each sanctioned by a different organisation, of which Joshua is in possession of three: the WBA, the IBF and the IBO. But from tonight, he may also be holding an award that, while no stranger to dispute, is at least dispensed according to public vote.

Joshua is hot favourite to land the BBC sports personality of the year award, previously held by such luminaries as Steve Davis, Torvill and Dean, Zara Phillips, Andy Murray and Kelly Holmes. To win the title as a boxer, these days, is no small achievement.

It’s not just that boxing is a sport frequently viewed as suspect, for both its inherent violence and its murky double-dealings. It’s also because heavyweight boxers seldom fight, and when they do meet in any significant bouts they are usually only available on pay-per-view on satellite television.

All of which means that the public does not get much opportunity to assess the personality of the sportsman or sportswoman in question. But that has not been a problem with the amiable Joshua, whose sunny disposition transcends his limited TV coverage.

Now 28, Joshua took up boxing only 10 years ago, as a rather wayward 18-year old who had spent time in Reading prison on remand for a crime he has described as “fighting and other crazy stuff”. Apparently he was looking at a maximum 10-year sentence, which suggests the stuff was indeed crazy, but the judge showed leniency and the fighter only had to wear an electronic tag for a year.

He says that the tag, boxing and an interest in reading turned him around. And, by his early 20s, he was fighting as an amateur at the 2011 European Championships. He lost in the quarter-finals, owing to a lack of training, because he had been arrested the year before after the police found him with 8oz of cannabis. He was wearing his Team GB tracksuit at the time. He was charged with intent to supply, which could have brought a substantial prison sentence. In the event, he received a temporary ban from boxing and, after admitting the charge, was sentenced to 100 hours community work.

“The arrest changed me a lot,” he said later. “It forced me to grow up and to respect my responsibilities. I’m not happy that I did what I did and there’s no way that kind of thing will ever happen again but, in a way, I’m glad it did because it woke me up.”

The following year he won the gold medal in super heavyweight division at the London Olympics.

It was an extraordinary turnaround in fortunes but Joshua has not looked back. While some Olympic champions – notably Muhammad Ali – have gone on to stellar careers in the professional ranks, it’s by no means a guarantee.

Britain’s previous Olympic winner in the super heavyweight division, Audley Harrison, failed to make the grade at the elite level. But Joshua was made of sterner stuff. His first few fights after he turned pro in 2013 were not unlike Harrison’s early bouts – easy victories within a couple of rounds.

But as the quality of opponent steadily increased, the lengths of the fights did not. It was not until his 15th fight that Joshua was taken past the third round. At 6ft 6in and 18 stone, Joshua is formidable. But unlike many boxers of that weight, he does not appear to have a spare ounce of fat. Indeed, he has the kind of six-pack that could make a Men’s Health model pull his expensively arranged hair out.

His looks, ease in the spotlight and a winning lack of arrogance make for a highly marketable combination. And perhaps it is no surprise that he has been the subject of much female attention. He split up with the mother of his young son not long ago, and was mistakenly cited by the boxer Amir Khan as his estranged wife’s lover – an accusation that Joshua corrected with a typically good humour: “Bantz aside,” he tweeted. “I hope you guys can resolve your situation or this is a hack as we have never even met! Plus I like my women BBW [big beautiful women].”

In the end, however, it all comes down to delivering in the ring. You can make magazine covers, appear on talk shows and be tweeted about by all manner of people, but if you do not have what it takes to stick it out when the going gets tough, then boxing is not the sport in which to seek fame.

Many boxing pundits looked at Joshua and saw a powerful puncher but a limited mover, someone who would get caught by a top-class opponent – and only then would it be revealed whether he had true staying power.

Although he was tested by a fellow Briton, Dillian Whyte, who had beaten him as an amateur, Joshua did not come up against a world-class boxer until he met Wladimir Klitschko at Wembley stadium in April this year. By then he was already IBF (International Boxing Federation) world champion, having defeated the holder Charles Martin inside two one-sided rounds.

But the equally towering Klitschko was an entirely different prospect. Although he had just turned 41, the Ukrainian was still thought of as a world-beater. He had held various crowns for more than 15 years, only losing to the Briton Tyson Fury two years ago. But with Fury suffering from depression and a positive cocaine sample, the title was back up for grabs.

Fury and Joshua make for a revealing comparative study. From Irish Traveller heritage, Fury was also nominated for sports personality of the year back in 2015, after defeating Klitschko. He finished fourth, having created controversy with a series of remarks deemed homophobic and sexist.

Anthony Joshua: ‘Staying humble, for me, means treating everyone with the same respect.’ Photograph: Levon Biss/The Observer

Fury appeared clueless in front of the camera, as if it represented the same attack-or-be-attacked threat as boxing. Joshua, by contrast, seems instinctively to grasp that television is his friend, the means of reaching his fan-base and extending it out to those people who could not be less interested in boxing.

But the night when Joshua met Klitschko was one for true boxing enthusiasts: 90,000 of them were packed into Wembley to see the Ukrainian put Joshua on the canvas in the sixth round. The boy from Watford, Hertfordshire, the son of a Nigerian mother and a British-Nigerian father, the young man who had taken up boxing to escape crime, suddenly looked as if he had met his match and finished second best.

He was wilting, maintaining a vertical stance through sheer willpower alone. But much to the surprise of seasoned observers, he gritted it out and put Klitschko down twice in the 11th round before the referee stopped the fight.

It was an epic match, and Joshua announced himself as not just a talented and powerful boxer but also a fighter of immense courage and determination. He showed something else, too, that does not always find its way into the boxing ring: humility.

He was generous in his praise of Klitschko and neither man had stooped to the kind of badmouthing antics that boxers sometimes engage in to sell tickets. The boy who once wore an electronic tag now has his own hashtag #Stayhumble.

“It doesn’t mean don’t aspire,” Joshua has said. “Every parent wants their children to better themselves. Staying humble, for me, means treating everyone with the same respect. I make time for the person who is homeless on the streets and the people who I meet on the Graham Norton Show, and I balance it out. That’s how I stay humble. Connecting with people.”

And connect with people Joshua certainly has. It is the reason that, barring the kind of voting upset that post-Brexit and post-Trump we can’t afford to dismiss, he is highly likely to become the nation’s favourite sportsperson for 2017.

If it does happen, it also seems a safe bet that the feet of the teetotal, chess-playing Joshua, who lives with his mother in their old council flat in Golders Green, north London, will remain firmly on the ground.

LIFE AND TIMES

Born in Watford, Hertfordshire, on 15 October 1989. His parents split up when he was about five.

After leaving school at 16, he began training at Finchley amateur boxing club, north London, with his cousin. Within three years he had been fast-tracked to the GB Olympic squad.

Worst of times In 2010, he was arrested for being in possession of 8oz of cannabis, while wearing his Team GB tracksuit.

Best of times Beating Wladimir Klitschko to win the world heavyweight title at Wembley stadium in April this year, in front of 90,000 people.