Anthony Joshua was the bad boy from a Watford council estate. Now he takes on Wladimir Klitschko with golden fists

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John Oliver knew the giant could punch when he heard a scream one evening. Sean Murphy was bent over double, swearing at the canvas as he tried to pull the pad off his hand.

It was swelling rapidly and the novice responsible was apologising over and again as he followed his trainer out of the ring at Finchley Amateur Boxing Club.

The big teenager had just joined and was only a couple of sessions in by then. 

Murphy and Oliver, two respected trainers, had been willing to take him in when he rocked up to their corner of Barnet in 2007, a tearaway with a difficult past and a promise that he would commit to something. 

Anthony Joshua has come a long way since taking up the sport a tearaway with a difficult past

Joshua looks into the eyes of Wladimir Klitschko ahead of Saturday's heavyweight showdown

Joshua's inner circle revealed to Sportsmail Joshua's journey from one persona to another

It was Murphy who, a few days later, gave in to the nagging and took the 18-year-old on the pads for the first time.

But almost immediately Murphy was rushing to get his hand into cold water.

'The thing with pad work is you do get problems with new boys,' Oliver tells Sportsmail. 'They might hit on the edge of the pad and it bends your fingers.

'But not this boy who had come in - he hit the pad perfectly in the middle with one of his first shots, bang.

'Sean starts yelling and this big lad is following him, saying 'sorry, sorry'. We were all laughing but then Sean has to go off to hospital so that's a bit more serious.

'My god, when we hear back from him it turns out he hasn't broken his hand - he's shattered it. Every single metacarpal was smashed, maybe broken in 10 places.

'Well, I'm 72, and I've been in rooms with Muhammad Ali and Mike Tyson – I don't think I've ever heard something like that. Even now, 10 years on, Sean has problems with that hand.'

Trainer Sean Murphy took an 18-year-old Anthony Joshua on the pads for the first time

Joshua's powerful right hand has had the capacity to cause damage since a very young age

The Watford-born boxer will be roared on by a 90,000 sell-out crowd at Wembley Stadium

David Ghansa isn't fully sure of his official title in the vast empire of Anthony Joshua, but he generally co-ordinates his training camps and keeps the operation ticking over.

He and Joshua go years back, to when they were kids, and Ghansa is the fighter's right-hand man and one of his closest friends. Except he doesn't call him Anthony or Josh or AJ like folk do these days.

'He is Fem or Femi to most of us who know him from back then,' Ghansa says.

It's a play on the second name in Anthony Oluwafemi Olaseni Joshua. The name is relevant because Femi and AJ are two sides of the same complex story, with Femi the teenage bruiser in Watford who was on a road to prison, and AJ is the multi-million pound brand, a 27-year-old billed as the greatest heavyweight for a generation and the respectful face of boxing.

The journey from one persona to the other, told to Sportsmail by members of Joshua's inner circle, takes in brutal beatings in Nigeria, a set of weights from Argos and courtrooms. Then there was the electronic tag, the stash of cannabis in his holdall, the vomit stains on his toilet and a private vow to Ghansa on Facebook that it was all going to change.

And it did.

Joshua goes by the name of 'Fem or Femi' to those who know him - a play on his second name

Femi was the teenage bruiser who was on a road to prison before boxing refocused him

AJ is the multi-million pound brand, a 27-year-old billed as the greatest heavyweight

The Femi tale dates back to Watford in 1989 and his birth to a pair of Nigerian immigrants. Joshua reckons his mother, Yeta Odusanya, a social worker, and his father, Robert, a Nigerian with Irish heritage, arrived in Britain in their early twenties and split when he was four or five.

He started out with his mother on the Meriden Estate in Watford, staying in a neat flat in a rough area with his two sisters and brother. 'He was always active,' says Ben Ileyemi, his cousin, who is a former amateur boxing champion and the man who introduced Joshua to the sport.

'He was always playing football or whatever. We used to scrap and I would get the better of him. Things have changed.

'We were messing around a couple of years ago and he hit me in the ribs. I never actually told him at the time but I was in pain for about four days. Imagine taking a scaffolding pole and wrapping a pillow case on the end, then getting wacked with it. That's what it is like.

'But back then he was just a big lad who wanted to be outside.'

Joshua has posted a picture of him being fed strength during his childhood on Instagram 

Mummy's boy: a young Anthony (left) with his sister and mum Yeta, who still lives with her son and is known as the boss of the Joshua family instagram

Joshua's life took a dramatic turn when he was 11. His mother briefly returned to Nigeria and took Joshua with her, enrolling him in a boarding school where, the story goes, he would wake at 5.30am each morning to fetch water.

'Sometimes the whole block would just get punished,' Joshua said recently. 'It might be the cane, or you would have to squat and hold it for 30 minutes.

'We got beaten, but that's my culture, beating.'

He returned to Britain after two terms and started at Kings Langley School, where his best performances came in PE - he ran 11.6seconds in the 100m in Year 9 and played as centre-forward for the football team.

'Femi still holds the Year 8 record for the 400m,' says his PE teacher, John Annett. 'He ran it in 60 seconds dead which is very fast for a 12-year-old.

'The fact he has become a boxer is still a bit of a surprise for me because I was convinced he could become a footballer.'

There was one notable incident in a school match, when Joshua was 16, that hinted of the trouble to come. An opposition player was winding him up and Joshua grabbed the boy by the neck and dropped him over his shoulder. Joshua was charged with ABH but escaped with a warning.

Joshua lands with a ferocious right hook against Dillian Whyte in December 2015

Gary Cornish hits the canvas and is one of Joshua's 18 opponents to suffer a knock-out defeat

'He wasn't a bad lad as such,' Annett says. 'He was disruptive and got lectured by the head a bit towards the end but that was about the limit of it.'

He left school at 16 and his problems escalated quickly when his mother moved to Golders Green and Joshua briefly stayed in hostels in Watford. He was drinking, smoking, partying and, in his words, 'causing creative mischief' as part of a gang of 40.

It is commonly reported that in 2009, when he was 20, he was placed on remand in a Reading prison for two weeks for 'fighting and other crazy stuff', but in actual fact it was around 2007. He has long refused to discuss the specifics of what happened, but it is known the fear of serious jail time prompted him to buy weights from Argos to bulk up in readiness.

His reprieve from a custodial sentence ultimately led him to move in with his mother again and from there he turned up at Finchley ABC that first time, complete with an ankle tag. His cousin, Ileyemi, was training there and brought along Joshua, who had started working as a bricklayer.

Joshua's current success is a far cry from the days of drinking, smoking and partying

Joshua celebrates with his dad after beating Charles Martin to win IBF World Heavyweight title

'His main coach was Sean Murphy and we would all just watch this great big lad,' John Oliver says. 'That raw power, the way he broke Sean's hand that time, you just don't see that.

'After one of those first sessions I told my partner, Carol, that I had just seen a future world champion.'

Ileyemi, who loaned Joshua £25 for his first pair of boxing boots, adds: 'He took to it so naturally. But I'll always remember one of his first sessions – he was so knackered he had to wait 15 minutes before getting in the car. Then as soon as he got home he threw up everywhere.

'You could see, though, that he was getting into it.'

David Ghansa recalls receiving a message on Facebook one night. 'It was Fem,' he says. 'He was telling me he wanted make a go of this boxing thing.

'I find it amazing to think back to that message now.'

A career in boxing beckoned for Joshua after his best school performances came in PE

The Watford-born boxer bought weights from Argos to bulk up in readiness for time in jail

Joshua made astonishing progress through the amateur ranks. He won the national ABA championship in 2010, turned down an offer of £50,000 to go pro, and then was recruited to Team GB. There would, in the space of four years up to London 2012, be another ABA title and a world championship silver.

He moved at unprecedented speed, despite his most publicised clash with the law in 2010, when he was arrested in possession of 8oz of cannabis, while wearing his Team GB tracksuit.

Joshua was given 100 hours community service and suspended by Team GB. 'Sean and I took him aside so many times to tell him to give up whatever he was doing out there,' Oliver says. 'That last one, though, was the real wake up call.

'He was doing his community service in north Finchley, on an allotment next to my house. I used to sit with him in my car when he was done and talk about what he was doing with his life.

'The way he responded to what happened, I couldn't be prouder.'

Within two years Joshua was the Olympic champion.

Joshua looks to cause damage to Italy's Roberto Cammarelle during his gold medal fight

Joshua poses with his gold medal having won the Men's Super Heavy (+91kg) Boxing final bout

The AJ tale is one of a man and brand travelling at blinding pace.

In even less time than it took for him to rule the world amateur scene, he is a world heavyweight champion, winning the IBF portion of the crown in less than three years. He is worth north of £10m, courtesy of the sort of endorsements that don't typically exist in boxing.

'As a guy he hasn't changed,' says Ghansa. 'He is still the same person, it's just that once he found the discipline in his life there has been no stopping him.

'But he'll still find an excuse if he loses at FIFA on the console – it will be the controller's fault. And he still watches all sorts of stuff on the telly. He once spent the weekend watching documentaries about the independence of Congo and telling all about it.

Joshua still lives at home with his mother Yeta Odusanya  in a council flat in Golders Green

'His current thing is missiles and North Korea. He'll be like, 'How long would it take to evacuate Sheffield?' He just goes through life all relaxed, but at the same time on this mission to be the best he can be.

'He still has all the same friends, still comes out with the same things.'

His treat for winning the Olympics was to buy himself an £800 motorbike. He also still lives in the same former local authority house with his mother. 'African mums are the boss and Fem doesn't argue with her,' Ghansa says.

Oliver laughs at the memories. 'He still refers to me as the Godfather and Carrol, my partner, as the Fairy Godmother,' he says. 'Just the other day he text her to say he had arranged tickets for us for the Klitschko fight.

'What a lovely lad he is, more than anything else. Nothing is too much trouble.'

The question is whether Klitschko, the old warrior, will be too much trouble, given he is so much better than anyone else Joshua has faced in a perfect professional career of 18 knockouts. He has looked excellent, but is yet to go past the seventh round.

Joshua will hope to demonstrate his incredible power once more at Wembley on Saturday

Joshua#s promoter Eddie Hearn has opted not to stand in the way of his fighter's swift rise

And now he faces the former ruler of the heavyweights, a 10-year champion. It is no secret that Joshua's promoter Eddie Hearn wanted to go slower than this.

Sometimes in boxing, though, an opportunity comes along that cannot be ignored. And sometimes a fighter comes along that goes against conventional wisdom. Is Joshua that guy?

As John Oliver put it: 'If he punches Klitschko like he punched Sean's hand, you'll have the answer.'