To see Usman Raja before a cage-fight is to see a man in his element. As scantily clad dancing girls parade around and fast paced techno-music blares through the venue, and rows and rows of mostly white working class spectators eagerly await the contest, Raja is in a side room prepping his fighters, sparring with them, and reminding them of the importance of technique.

It is a brutal and intensely physical sport. One of his fighters, a towering muscular Pole reaches the heavyweight title match that day, during which he pulverizes his opponent with a volley of powerful kicks and punches, soon knocking him to the floor. "Knee to head," Raja exclaims as he enters the ring to hug the victorious fighter.

Raja is also behind what UK officials say is the most successful effort they have seen to de-radicalize some of the most hardline Islamist extremists being released from UK jails, including around a dozen convicted terrorists who recently completed their prison sentences.

He has used cage-fighting as a key tool in this work. Raja says teaching the former terrorists cage-fighting skills has proved a remarkably effective way of breaking them out of their al Qaeda mentality, opening up their minds to his counter-extremist message, and providing them with a sense of discipline and purpose.

Raja knows how to connect with his charges. Like several of them he is from the tough neighborhoods of east London, once subscribed to fundamentalist views himself, and Raja says he came close to fighting Jihad in Bosnia in the 1990s.

His life story shows the young men he is working with that they can transform their own lives by embracing a spiritual, humanistic, and tolerant Islam.

As a teenager Raja, by his own account, had run wild. He had at first lived in east London but after his father left the family when he was 11, he and his brother Suleiman were brought up on a public housing estate by his mother in Farnborough, a white working class town south west of London dominated by the presence of nearby military barracks.

As a single parent, she struggled to provide for them. Raja, as one of the only non-white kids in town, often suffered racial abuse. It started, he said, when he was about eight.

"One guy once asked me "has someone spread excrement on your face?" When I was 13 another guy came up to me and threatened to smash a milk bottle on my head," Raja said.

His response was to fight back. "The reaction was if I punch him in the face he tastes his own blood -- it's going to stop him being racist," Raja recalled.

His father came back into his life when he was 16. For a period he and his brother moved up to Huddersfield in northern England to live with him. "In order to civilize us he got us involved in Thai boxing," Raja said.

The 16-year-old Raja had quite an attitude but, he says, he soon got a reality check, which saw him learn the virtue of self-discipline.

"I remember in my third session my Thai boxing coach lifted his elbows, allowed me to kick him as hard as I could in the ribs while sparing, grabbed my head, kneed me in the head and broke my nose and that woke me up," Raja told CNN. From then on he trained six days a week. "Going into that reality makes you check yourself," he said.

At around the same time Raja became inquisitive about Islam for the first time. Though his mother prayed five times a day, religion had never been an important part of his life.

"I had looked at Islam and thought wait a minute, you've got a messed up religion where women have to cover their heads and stay at home, while men are out doing what they want," he recalled.

Like many born again into Islam with little exposure in their youth to Islamic teaching but a desire to deepen their faith, Raja gravitated towards Salafist-fundamentalism. "That's just what was out there," he said.

Salafism is a literalist approach to Islam that has taken on different forms across the Muslim world but followers seek a return to what they say are the true values of the religion before these were corrupted by Western modernity and other influences. While many Salafists are Amish-like in focusing all their energies on living their religion, a small but significant number, particularly in the West, have in past decades become politicized.

"It was all about Jihad in Afghanistan, Chechnya and Bosnia," Raja said. There was widespread anger in the Muslim community about the massacres of Muslims by Bosnian-Serbs in the Balkan country.

"I found myself feeling that injustice and wanting to go there and fight that injustice," Raja recalled.

"My dad was willing to fund that but the mosque committee stopped him," Raja said.

He channeled his energy into fight training, eventually becoming one of the UK's top cage-fighters. He attended a graphic design course at a college back in Farnborough and earned occasional money as a bouncer, but his priority was fighting.

"You start to glorify yourself," Raja recalled. "Over time you realize that ego is the biggest opponent."

The sport was fast taking root and its leading lights were beginning to become lionized like gladiators in Rome.

Many of his friends from fighting were white working class who in the early days made up the majority of the sport's fan base and fighters.

Many of them also lived hedonistic life styles: women, nightclubs, and cars. "Though I was a Salafist, it wasn't like I was puritanical," Raja said. "For me it was always more about the oppression of Muslims overseas than Sharia law."