It’s not something most of us could imagine ever saying, but Chrystal White truly believes that being diagnosed with HIV saved her life.

After sinking into a world of drugs and prostitution as a teenager, she spent years not caring if she lived or died until some terrible news turned her world upside-down – and gave her a reason to go on.

Chrystal had been left blind in one eye after she was glassed by a robber who attacked her when she was buying drugs. But even that wasn’t enough to put an end to her life on the streets. It was only when she got HIV that everything changed.

“It may sound strange but the way I look at it, being diagnosed with HIV was a blessing. I honestly think if I hadn’t been, I’d be dead from drugs by now,” says Chrystal, 26.

When she talks about her “chaotic” childhood, it’s easy to see why she ended up with the life she did.

“There wasn’t a lot of love in our house – or food. We were always hungry,” says Chrystal, who is one of 10 children.

“I remember once eating toothpaste and dry pasta because we were so hungry. We learnt how to shoplift when we were young – sweets, crisps, anything to keep the hunger at bay.”

Chrystal’s parents split up when she was 12, and she ended up living with her brothers in their dad’s flat in the red light district of a Midlands town.

She started smoking, tried alcohol and cannabis and skipped school.

Chrystal made friends with three girls in her year and they started shoplifting. One evening they went out and her pals admitted they were prostitutes.

Chrystal says: “I’d stand on the street with them, but I was too scared to do anything. They tried to get me to do what they were doing, but I wouldn’t. I was still a virgin.”

But the financial temptation got the better of her and, eventually, Chrystal started having sex with men for money.

She remembers the first time with a shiver of revulsion.

“I was petrified,” she says. “The man drove me in his car to a dark country lane and I had to turn my head away while he was on top of me. He made my skin crawl and it hurt.”

The man paid Chrystal £100. “Afterwards I drank and smoked pot until I’d obliterated my feelings,” she says.

Over the next few months Chrystal and her three friends had sex with men for money in cars regularly, in alleys and bushes. As soon as they’d made £200, they’d call it a night.

“Clients knew we were underage but that’s what most were looking for,” she says.

“I hated what I was doing, but I loved the money. It meant I was able to wear fashionable clothes not hand-me-downs and I never went hungry.”

But Chrystal’s life took an even darker turn when her friends introduced her to crack cocaine. She was soon hooked.

By then Chrystal was 15 and her life was out of control. On one terrifying occasion she was kept against her will in a basement flat by a man. She decided the drugs had to stop if she was to stand any chance of turning her life around. By then she was living in London.

“I stayed off drugs for more than a year,” she says. But temptation proved too much.

“I was using crack to get high and heroin to come down, working flat out to fund my habit.