Pulled over by cops for speeding in his Mercedes Benz in London in January 2011, the officers found 8oz of cannabis concealed in his sports bag.
They had little difficulty identifying the then-Olympic hopeful boxer — Anthony was wearing his Great Britain tracksuit at the time.
He was charged with drug dealing and it seemed like the end for a promising young sportsman.
Joshua and his mother
The Watford-born fighter would later remember of those days: “I wasn’t with the best group of people. It was all about how I looked, my clothes, clubbing, girls.”
He was a long, long way down the wrong track. But he has traced his way back to the road to sporting glory.
The very year after the bust, an Olympic gold medal was hanging from his muscled neck.
An imperious 18 knockouts in 18 professional fights followed.
Joshua as a baby with his mother and sister
On Saturday, beneath the hallowed arch of Wembley Stadium, a partisan crowd of 90,000 — and Ukrainian giant Wladimir Klitschko, considered one of the greatest heavyweights of all time — will await him.
The prize, THREE heavyweight world titles — the IBF one he is defending as well as crowns from the IBO and WBA.
Anthony, 27, promises to “unleash hell” against Klitschko, 41 — who like himself, towers 6ft 6in tall.
A purse of some £15million awaits each fighter, win or lose, in a battle expected to smash pay-per-view records and gross a total heading towards £50million — making it the most lucrative in UK history.
One of the apparently few who will not be watching is his mum, Yeta. She cannot bear to see her boy fight.
But she recalls one of his trainers in the early days saying: “You know what, Mum, your boy is going to be a world champion one day.”
“I was like, ‘What’s he talking about?’ I didn’t take it quite seriously until he qualified for the Olympics.
“When he won the Olympics, I didn’t really want to watch it, because I don’t really like watching him, I was sat down and that was the longest nine minutes of my life.
“I had a piece of paper over my face until the end then when I heard he won I was just so excited, I started jumping up and down. It was very nice, a very proud moment.”
These days Anthony also has another family member he hopes to make proud — a son called Joseph Bayley Temiloluwa Prince Joshua, known as JJ, now 18 months old.
Joshua chats with his mother
While Anthony is no longer with JJ’s mum — dance teacher Nicole Osbourne who he has known since school — he is a besotted dad.
The champ explained: “It’s a beautiful thing as he gets older and you start seeing his personality.
“I look at what I am creating. Giving my little boy a better opportunity than I had.”
Anthony Oluwafemi Olaseni Joshua was born on October 15, 1989, in Watford, Herts, to Yeta from Nigeria and dad Robert, who is of Nigerian and Irish descent.
The couple split up when Anthony was four or five and along with his brother and two sisters, he grew up on the tough local Meriden Estate.
He attended local primaries until the age of 11 when his mother relocated the family to Nigeria, where the lad was enrolled in a boarding school renowned for its iron discipline.
Anthony recalled: “Every morning we would be woken up at 5.30 and then we had to fetch water.
“You had to heat the water up by putting a hot iron in it, then you had to make sure all your school clothes were cleaned and ironed. The discipline was tough.
“Sometimes the whole block would just get punished. It might be the cane, or you would stand and squat and hold it for 30 minutes.”
Joshua celebrates with his father and aunty after a fight
But after just two unhappy terms, a miracle occurred. Mum Yeta decided to move the family back to Britain.
Anthony describes the moment she arrived at the school gates to take him home as “better than winning the Olympics”.
Back at Kings Langley School near Watford, Anthony became an accomplished athlete. He ran 100m in 11sec at 14 and was a gifted footballer.
And it was on the football pitch that, aged 16, he had his first brush with the law.
He later explained: “I was quite a good striker at school but during one game this guy was trying to wind me up. I got him round the neck and threw him over my shoulder.
“I didn’t know my own strength and he didn’t land too well.
“Incredibly, it went to court and I was charged with ABH. Luckily, they ended up giving me a slap across the wrist.
“It was time to stop playing football, though.”
That brawl was the start of a descent into a dark period of street and bar fighting and petty crime.
He explained: “Even if you don’t drink, people get in your space and it easily kicks off. So, yeah, it kicked off a few times and I got arrested.”
But in 2007 when he was 17 his life changed when his cousin, professional boxer Ben Ileyemi, took him along to Finchley Amateur Boxing Club in North London. Also there that night was ex-European super-featherweight Spencer Oliver, whose dad Jimmy and uncle Johnny ran the gym — and who has never forgotten what he saw.
The Sky Sports pundit said: “Ben had brought him in purely to get off the streets.
“His physical presence stood out straightaway. Josh looked raw and strong and I can remember my dad saying he was going to be special.
“But up to then — Josh really was living a bad life. When he arrived I’m pretty sure he was on an Asbo at the time.”
Relentless hours in that gym saw him hone his near-18st bulk into a fighting machine.
Being struck by his right fist is said to be like being hit by an 11lb sledgehammer at 30 miles per hour.
Yet his old ways kept calling him back.
In 2009 he found himself on remand in jail in Reading, Berks, for “fighting and other crazy stuff” but he was released with an electronic tag on his ankle.
He later admitted: “I was on a tag for 14 months. And I had to sign on at the police station three times a week.
“Part of the conditions of my release on tag was that I went to college and learned a trade – so I took up bricklaying.”
At the same he was of course still boxing and his amateur career was soaring.
He became British Super Heavyweight champion in 2010 and had gold at the 2012 London Olympics in his sights, when he contrived to self-destruct once more.
Charged with possession and intent to supply of cannabis “while cruisin’ in my Merc” in Colindale, North West London, the big man remembered: “I got suspended from Team GB and very nearly didn’t make the Olympics. I would have got ten years in jail.”
But after the dealing part of the charge was dropped, he escaped with a 12-month community order and 100 hours’ unpaid work helping pensioners with their gardening on an allotment.
And he finally understood that he had run out of second chances.
Anthony recalled: “I realised that I could either fight and get into trouble on the street, or I could fight and get paid in the ring. I chose the ring.”
An Olympic gold in the super-heavyweight division soon followed — along with an MBE, an ever-growing collection of selfies with famous fans and now, of course, tomorrow’s prize payday.
But boxing means far more to Anthony than any of that.
He declared of the sport: “It teaches you how to be a man. Discipline. Knowing to say ‘no’ to certain things and knowing what’s right.”