"I'm a work in progress," says Anthony Kelly, former career criminal, long-term drug abuser and one-time star trainee in TV chef Gordon Ramsay's Bad Boys' Bakery. Before taking part in last year's surprise-hit reality TV programme, Gordon Behind Bars, in which Ramsay set up a professional bakery in the bowels of London's Brixton prison, Kelly, 34, had spent a total of 16 years in a variety of jails around the country serving time for burglary, drug dealing, stealing from heavy goods vehicles and innumerable other felonious activities.

Now, a year after the series ended, the fast-talking cockney's life has taken a dramatic change in direction. For the first time since he was 10 years old, and after a long stint in a rehabilitation clinic in Devon, Kelly is clear of drugs.

"I never knew life could be this good," he says when we meet in Anchor House, a former seafarer's mission that serves the needs of homeless people in Canning Town, east London. He smiles a lot as we chat and looks much fitter and healthier than he did on TV. "No drugs, no crime. I can't imagine going back to the way I lived before," he says.

It would be hard to imagine anyone living the way Kelly did before. He was born in the East End of London in 1978 and brought up in Canning Town with his four siblings. His mother was Glaswegian; his father a seaman from Liverpool. Both were alcoholics.

"They fought constantly," he says, "I mean with bottles, knives, a tin-opener, anything they could get their hands on, when they were drunk. Once, my mother put a hot iron on my dad's back when he was asleep and he almost jumped out of the window. The bath was full of mouldy towels. The kitchen was covered in filth. It was squalor."

He recounts how, as a six-year-old, he did "bob-a-job, a Saturday job, washing cars, even penny for the guy, anything to get money for booze for my mother. When she was drunk, I could just run on the streets. It was more comfortable out there than it was in that shithole of a house." He started "smoking puff" when he was seven, and by 10 he was sniffing cocaine and passing painkillers off as ecstasy tablets at rave parties. Perhaps it was inevitable he would end up in the care system. "They put me into care for not going to school, but once I was in care I never went to school ever again," he says. He ran away from care homes dozens of times, sleeping in cars, sheds, squats, and committing relatively petty crimes to survive. He was 12 when his mother, aged just 39, died from alcohol-related illnesses, and his criminal behaviour escalated. At 15, he was sent to a young offenders' institution for theft, and his future as an established "prolific and priority offender" was secured.

Dysfunction-causing issues that have festered and fed criminality and antisocial behaviour from an early age often become so deep-rooted that by adulthood they are almost impossible to resolve. To change such a damaged life takes courage, commitment and, above all, support. How much of Kelly's turnaround does he owe to his prison encounter with Gordon Ramsay?

"I owe Gordon a lot," he says. "He was totally genuine in the prison. Away from the cameras, he was as good as gold. He told us about his own troubles – his brother has addiction problems and his old man was an alcoholic. But as much as I got from that experience, it was this place that has really given me what I needed to change."

Kelly is referring to Anchor House; he has been in and out of its doors since his days on the streets as a child. "These people have never turned me away," he says. He explains that he made a decision to change before he went in to serve his last prison sentence. "I was sick of living in constant embarrassment and shame; sick of being a criminal causing untold misery," he says. The people who run Anchor House offered him a way out. "It was them who paid the £10,000 for my stay in rehab. Without them, I don't think I would have made it."

And what about Ramsay's programme? "What he did is highlight the fact that there are plenty of people in prison who want to change, and he gave a few of us the chance to show that. I was never going to be a cook," he says, laughing. "But I wanted to prove myself to the doubters. Some of the guys on the course went on to work in restaurants. A couple ended up back inside. It's hard to change when you've been in and out of prison all your life. Gordon gave us a chance to show we were willing. But not everybody gets the chance that I've been given. I'm lucky I've got the support I need to keep this up, and now I'm determined to put my experience to good use to help others who've been through it like me."

Post-prison, Kelly has worked with prisoner peer-mentoring charity the St Giles Trust and done a stint as an actor at the Theatre Royal in Plymouth. "I only went there as a volunteer helper [as part of his rehab programme] and they got me up on stage, acting," he says. Currently, he is undertaking training, supported by Anchor House, to become a "lifestyle architect", a sort of life coach-cum-counsellor for those struggling with troubled and troublesome lives.

In the meantime, Brixton's Bad Boys' Bakery continues to thrive. Since the kitchen and the training programme were taken over by welfare-to-work provider Working Links, the bakery has provided more than 15,000 products to 14 branches of the coffee house chain Caffè Nero.

Our conversation at an end, Kelly and I shake hands and I wish him luck. But just before we part, I ask him: "So do you think you really have changed?" He laughs again."Oh, mate," he says, "I'm doing my best. As I said, I'm a work in progress."