Marching him towards the segregation unit, they passed an ambulance and Tony saw his victim lying motionless on a stretcher, a prison officer taking photographs of him.

The ambulance's lights and engine were off, and a paramedic was standing outside smoking a cigarette.

"Is he all right?" Tony asked.

As the prison officer looked at him and bowed his head, Tony assumed the worst.

Fast-forward seven years and Tony is now living in Chartham, having started a brand-new chapter in his life as a happy, healthy 45-year-old.

But he has been down a long and winding road to get here.

Born to parents struggling with drug and alcohol addiction, Tony went through heroin withdrawal as a newborn, and spent his first years being raised by relatives in Ashford and Folkestone.

"I can't put my parents down," he said, "because everyone's struggled at some point in their life with something, and that was their struggle."

Aged six, Tony was taken into emergency care - the first of about 50 foster homes and care homes he would be passed between in the years that followed.

At one point, he fell victim to serious physical and emotional abuse and was deprived of food and sleep.

"Once, my hand was burned with an iron," Tony recalls.

"I didn't trust anybody. The people who were meant to protect and look after me hadn't.

"I'd gone from one challenging, chaotic situation into an abusive one.

"It left me very resentful, unable to function within a family-type setting."

Tony was eventually adopted by a large family in Selling - the Beaumonts.

A loving couple with five children of their own, they adopted both 11-year-old Tony and another young boy, who had been left with severe brain damage after being beaten as a child.

"This amazing family took us in and loved us and cared for us," said Tony.

"At the beginning it was amazing and I was really grateful.

"I was excited to be in the countryside, and spent a lot of time playing in the woods and making tree houses,"

An intelligent teen, Tony began to excel at Canterbury High School. But he soon began to rebel, committing increasingly serious crimes.

"I was stealing from home, shoplifting, bunking off," he said.

"I got a buzz from it. I'd been through the worst people could throw at me, so I had no fear of people.

"I didn't feel like I was part of the world. I felt like I had no identity.

"I was the kid in care. And being a kid in care, you're always treated differently by everyone - peers, teachers, social workers.

"I found a little clique in school, and we terrorised the streets of Canterbury. We committed some horrible crimes.

"I was doing a lot of running away, living with the travelling community.

"Because I struggled so much with identity, I was always drawn to people who seemed to feel like I did. The people on the fringes of society - the travelling community, the drug users, the bullies."

Tony's behaviour drove a wedge between him and his adopted parents, and at 14 he voluntarily went back into care.

"They tried their best," he said. "I remember my adoptive dad driving at all hours around Canterbury looking for me, but I was gone by then.

"I understood the pain I was putting my adoptive parents through, and so going back into care was like a way to protect them from me."

But Tony's crimes continued to escalate, and at 15 he was sent to Feltham Young Offenders Institution where he served several sentences, mainly for burglaries.

"Every time I went to prison I used it as a kind of rehab, did all the courses I could, got as fit as I could," he said.

"I wasn't on the streets running riot. It gave me room to breathe, three meals a day, and I thrived within that structure."

But once back out on the streets, he took to selling drugs around Thanet.

He soon began doing "boat runs" to France, buying cheap duty-free alcohol and cigarettes to sell in Kent.

"It was exciting to begin with," said Tony. "I was making lots of money.

"It was fun - jumping on planes to Ibiza, going to New York and Norway, Istanbul. At 19 I smuggled khat - a leaf that people chew - to New York, to Somali gangsters.

"I enjoyed the danger. When you're selling drugs a lot of people suck up to you. I found an identity in drug dealing and enjoyed that for a while until my mid-20s.

"But I began to realise I was surrounded by people for the wrong reasons."

"You're just trying to feed a habit. It robs you of your humanity and you become a shell of who you were..."

Deeply unhappy, Tony began using heroin - carrying out crimes like shoplifting to support what rapidly became a serious addiction.

"It robs you of so much so quickly," he explained. "It didn't take long before I was losing everything.

"I became more chaotic, dangerous.I was robbing drug dealers, and taking more and more drugs.

"My health suffered really rapidly, my cleanliness. When you're in addiction, you lose even those basic survival functions.

"You're reduced to nothing. You're just trying to feed a habit. It robs you of your humanity and you become a shell of who you were."

Tony relocated to Canterbury in his late 20s.

But despite attempts at rehab his addiction persisted, and he began living on the streets.

In November 2013, at the age of 38, Tony was jailed for burglary - after breaking into a property to find somewhere to sleep, and stealing a purse.

"I wanted to go," he said. "It was kind of an escape. I wanted to get rid of my habit.

"Prison before had always been a bit like rehab - I could get healthy, go to the gym, do some classes."

But Tony arrived at Rochester Prison to find it pervaded by a drug he had never previously encountered: Spice.

The synthetic drug is well-known for leaving users in "zombie" states, and is said to be "more addictive than crack cocaine".

"The whole prison system had broken down because of this drug," said Tony.

"It was just chaotic, and very frightening. The violence was unbelievable - I'd never seen anything like it."

Meanwhile, Tony found himself targeted by prisoners who wanted to get their hands on the medication he was given to help wean him off heroin.

He recalls trying to get isolated away from the violence.

"This guy had been threatening me for a couple of weeks," he said. "I'd thrown a chair at an officer and punched a prisoner in an effort to get segregated.

"I'd tried everything but it didn't work. I didn't want to be a victim any more, and I was afraid.

"Eventually, I met violence with violence."

One day, armed with a plastic prison knife, Tony crept up to his alleged intimidator while he sat at a table.

Aiming to perforate the man's cheek, he missed and instead plunged the utensil into his neck.

"I can't justify what I did," said Tony.

"I meant to stab him, but I wanted people to leave me alone - to send a message out and feel safe.

"So there was a part of me that felt kind of glad, that wanted him to feel as frightened as I did."

Miraculously, the knife missed the man's jugular and he survived after having the implement surgically removed at a London hospital.

Tony was arrested on suspicion of attempted murder.

He later pleaded guilty to wounding with intent to commit grievous bodily harm, and was sentenced to eight more years in prison.

But it was then that he began his journey towards completely turning his life around.

Tony credits this to finding religion.

After stabbing his fellow inmate, he had prayed hard for the man to pull through - describing his victim's survival as "an absolute miracle".

A couple of days after the attack, he got hold of a Bible and says the faith he found within it helped guide him through his recovery.

"I came up against it," he said. "You're a born-again Christian in prison, and people didn't know how to take that.

"I still struggled with bullies and drug dealers and it wasn't always easy.

"But I found hope. I started making different decisions."

With the help of a recovery programme, Tony managed to come off drugs, and began to get his health back.

"I trained hard and got super fit, after all those years of drug abuse," he said.

"I started studying, then I got my drug counselling diploma. I was hungry for knowledge and to move forward. Every opportunity I got, I grabbed it.

"I did a complete 180. It was a complete transformation.

"Suddenly I had an urge to do right, and to look out for people and help support them."

In a bid to relearn how to communicate with people, Tony began clipping other prisoners' hair, and began holding bible study groups in his prison cell with other inmates.

In December 2018, after serving just over five years of his sentence, Tony left prison a changed man.

He's since become part of a city church, where he has built a homeless outreach team that has delivered hundreds of meals to Canterbury's rough sleepers.

"I have an amazing team - including two teachers, a police officer and a college tutor," he said.

"It's crazy. I've gone from being a criminal to being around people I would have never thought I'd be able to associate with or feel equal to."

Last February, Tony moved to a house in Chartham, and had just qualified as a tree surgeon when he fell off an electric scooter and broke his leg in four places.

His injury may prohibit him from scaling trees, but he is determined to set up his own tree surgery firm, along with an online ministry to help other people and prisoners.

He travels to churches, schools and universities to share his story, and hopes to one day write a book about his life.

He has also helped raise thousands of pounds for Canterbury homelessness charity Catching Lives, to "repay" help it gave him - and has reconnected with his adoptive family, birth family, and various foster parents.

"I've made a lot of amends," he said.

"I still struggle with dark thoughts sometimes. I came through a lot of stuff as a kid."

But Tony says his faith his helped him understand the positives he has gained through his negative ordeals.

"Every single experience has taught me something," he said.

"Even the abuse gave me so much. It taught me empathy, and not to accept things at face value.

"I want people - especially care leavers, people who have struggled with drugs, who have been victims or abused, or are in difficult marriages or relationships - to understand how much they've got, and how much they've learned, and the qualities they've gained through surviving."

A short film in which Tony discusses his story (Video: Eastgate Plus/YouTube)

Tony also remembers all the "precious souls - homeless people and addicts that have passed away through overdose or failing health in our city centre".

"I ask for the public to treat these guys with empathy and compassion," he said.

"We have lost so many and many of them have lived such chaotic lives that they have died alone. So prayers and thoughts are with them."

Tony views his own story not as a tragedy, but as one of hope.

"I want people that read about it to understand that every single one of them possesses something extraordinary, and can do amazing things," he said.

"I was broken and homeless and very unhealthy. I had all sorts of problems with drugs and my health.

"But it's coming back. You can come back."

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