THEY pulled his shirt over his head with the sleeves still buttoned at the wrist, so he couldn't move his arms. Then they yanked his trousers and his pants down to his ankles. Then they started to hit him. Seriously.

Painful blows arrived from every direction. Fists, elbows, knees, feet all went in hard.

Six burly Borstal warders against one scrawny 17-year-old lad in an old stone cell barely big enough to swing a cat and from which there was no escape.

It was hardly a fair contest, but then it was never meant to be. When you get involved in a jail riot, innocent or guilty, and you lose, you take what's coming.

And it came too. As savage a beating as Mark Johnson had known in his young life. When it was over they left him, naked and battered on the rubber tiled floor.

It's possibly not the sort of experience many of Prince Charles' special advisors have gone through, but then the story of Mark Johnson, from heroin addict to friend of HRH, is a quite extraordinary one.

Part of it is told in his autobiographical book Wasted (Sphere, £12.99), but there is almost certainly more to follow. Because life today for the boy from the Kidderminster council flats has a direction, purpose and quality that must seem a universe away from where he was born.

He's going places and it's not into rehab or prison.

Having hauled himself from the depths of drug-fuelled despair to winner of the Prince's Trust Young Achiever of the Year award, he's being promoted as an inspirational individual. An example of no matter how low you go, you can make it if you really try.

"Prince Charles said he is enormously proud of me," said Mark. "But I have told him that he saved my life."

The Prince and the petty criminal came at life from two different angles.

Mark spent his formative years growing up in some of the roughest areas of the carpet town. In deference to those who may have been the Johnson family's neighbours I won't mention the roads. But people who were around at the time may recall his mother, who was an ardent Jehovah's Witness, and his father who was big and strong, dressed like a cowboy in lean blue jeans and checked shirts and was away from home a lot building power stations.

When his father came home he drank and combined with his mother's rigid view of life, this led to fights. Sometimes in the street outside their house. The violence spread to their children and young Mark was in frequent scraps at school. First at Lea Primary and then Comberton Middle. "Fighting was all I knew," he explained.

He then tried art college - "If things had turned out differently, I would have really liked a career in art and design" - but by the end of the 80s he was taking drugs, thieving and getting into serious trouble.

Mark was among a gang of six Kidderminster lads who attacked some out-of-towners' after a dispute, which didn't initially involve them, in a town centre wine bar. Two of their victims were left in a coma and he ended up handcuffed to a warder in the dock at Worcester Crown Court charged with violent disorder.

The sentence was 19-and-a-half months in custody and that's how Mark Johnson came to be in Portland Borstal, Dorset.

The beating he received from the warders followed a riot after someone tried to smuggle a sandwich out of the kitchens.

"Actually we were just 10 kids who wanted their breakfast," he recalled. "But as far as the authorities were concerned, we were a riot."

Sadly, the borstal experience did not stand him in good stead and within two months of release and high on drugs, Mark was involved in a violent robbery in a Kidderminster toilet, during which an elderly man was stabbed. He didn't carry the knife, but at Worcester Crown Court the judge jailed him for two and a half years for "a despicable crime".

After his release, Mark Johnson's life went into free-fall. For a while he lived in Birmingham with a "crack-head prostitute" then, following a nervous breakdown, moved to his mother's new home in the Lake District.

The location may sound idyllic, but life's reality was certainly not.

He hitched up with a heroin-addicted traveller, by whom he fathered a son, and began taking drugs in industrial quantities.

Amazingly, he completed a course as a tree surgeon and for a while worked in London, pruning trees at 11 Downing Street and St Paul's Cathedral before he was sacked because his drug abuse made him so weak.

"For almost a year I was homeless in London's West End," he said. "I slept rough in doorways and parks and had a £300-a-day crack and heroin addiction, which I funded mainly through crime."

He was down to seven-and-a-half stone and covered in the trade marks of his abuse, when a Turning Point worker found him in a doorway.

With remarkable willpower, and tremendous support from a lot of people, Mark has not taken a drug for seven years.

With help and a loan from the Prince's Trust he set up his own tree surgery business and became involved in helping addicts return to society.

In 2005, he was made the Trust's Young Achiever of the Year and won the Daily Mirror's Pride of Britain Award. The Big Issue featured his story, Prince Charles shook his hand and he's been to Clarence House three times.

But there's more. Mark is now a special advisor to the Prince's Trust and is currently piloting a new scheme that involves the mentoring of young offenders by ex-offenders.

He is also the first ex-offender on the board of the National Probation Service. "There's so much going on at present," he said. "So many different things to do."

Best of all, he's still alive.