Last updated at 09:37 01 March 2007

Less than a year ago, Kerstine Bury, 32, was homeless and working as a heroin-addicted prostitute. It was a huge fall from grace for the Catholic-educated schoolgirl who had been brought up by her businessman father Fred and his wife Sue in Maidenhead, Berkshire. Desperate to save their daughter, they paid £50,000 for her treatment at a private addiction clinic.

Here, in an alarming account, Kerstine tells CLARE CAMPBELL that it all began with just a single cannabis joint:

As I lay in a haze of semi-consciousness, I heard a man's voice saying: 'It's OK...she's just a junkie.' I felt someone lifting my eyelids to see if I was awake but I was too terrified even to breathe as I prayed for him to go away. As I heard his footsteps fade, I lay there motionless, trying to understand what had happened.

Then I realised. I had been raped by a gang of maybe eight men who had cornered me, and I had been too weak and too high on heroin to defend myself. I had struggled and my body was bruised and sore. But that was nothing compared to how I felt about myself psychologically. How had I let myself sink so low? For nearly 18 months I'd been living

For nearly 18 months I'd been living on the streets, homeless and so addicted to heroin and crack cocaine that I had traded my body for money. I felt so full of self-loathing that I wanted to die.

Suddenly, however, the thought of my seven-year-old son forced me to my feet. I could not let him down any longer. He was being looked after by my parents - who had been given custody of him after I became a drug addict three years earlier. I knew that, finally, something had to change.

As I wandered back to my parents' large family home, my thoughts returned to when I was little. I'd been so happy as a child, playing with my older brother at home.

My father had worked long hours building up a successful manufacturing business, and had also invested in property, but my parents had always found time for us and I'd enjoyed a typical middle-class childhood.

Like all little girls I'd loved horses and was thrilled when my father said I could take lessons. He was always generous and would have done anything for us.

My school life was great, too - I attended a Roman Catholic grammar school - but then, at the age of 15, I tried a spliff of cannabis at a friend's house and my life changed for ever.

I had been anxious about my GCSEs. I needed to get high grades as I wanted to please my parents and to be the 'good' girl they'd always encouraged me to be.

But that first hit of cannabis was like nothing I'd experienced before. I felt chilled, relaxed, and my exams didn't seem to matter any more.

Now, I truly believe that if I hadn't smoked that first cannabis joint I would never have gone on to harder drugs, and my life would never have spiralled out of control in such a self destructive way.

People should never under-estimate the serious implications of smoking cannabis. I quickly became addicted to the feeling of being out of control, and once I'd experienced my first high I was desperate to find something that would give me an even better one.

I started smoking cannabis regularly - my older friends could get their hands on the drug very easily. They also gave me LSD.

At 17, I was forced to take a year off school because I had a bad riding accident and broke my neck. I was in hospital for several months.

When I got out, I continued using drugs, often smoking several joints a day, as well as taking acid at the weekends. My drug addiction was starting to control me.

A year later, having been accepted into college to follow my dream of going to university, I dropped out. My father was terribly disappointed, but as he could not bear the idea of me being on the dole he continued to support me, giving me an allowance of £100 a week.

Because of his generosity, life was good. I thought I was in control. I set up a music studio in a flat owned by my father and would invite friends round to make recordings. I had always been interested in music and wanted to become a songwriter.

As I was cushioned by my parents' money I was very self-indulgent, going out clubbing and by now taking speed and ecstasy. I thought I was happy - but the feeling only lasted until the next high. My drug use grew and grew, until it was costing several hundred pounds a week.

My parents suspected something was wrong - but I just lied to them and to myself about my deepening addiction.

My behaviour was changing. Instead of having proper relationships with men, I was falling into casual affairs with other drug-takers. I became pregnant at 23.

Pregnant

Dad had always warned me about pregnancy before I was ready to start a family, so I was terrified the day I had to tell him: 'Dad, I'm going to have a baby.' Although I could see how upset he was, he said it was too late for him to be angry and that all he could do now was help. My mum hugged me and said we would cope together.

I loved being pregnant and saw my future child as a real incentive to get clean. I didn't touch drugs throughout my pregnancy and the moment that the doctor handed my son to me was the best of my life. I called him Marley after Bob Marley, whose music I had always loved.

I had told Marley's father that I was pregnant, but he did not want to be part of his upbringing. I didn't care. I was determined to be a good mother and to stay off drugs.

At first it worked. Instead of smoking dope I would take Marley to the park, then spend the afternoon playing with him. But the temptation was returning. Six months after giving birth, I smoked heroin for the first time - supplied by an ex-boyfriend.

I always promised myself I would never touch harder drugs. But within moments of smoking heroin, I was completely hooked.

Within two weeks I was suffering physical pain, vomiting if I didn't have it. At first I took heroin three times a week, then it was several times a day - I was spending £500 a week on my addiction.

By the age of 25, I was on crack cocaine. I was introduced to the drug by a computer consultant I met at a party who told me: 'Heroin just takes you down. If you want to go up, take crack.'

Looking back, I feel terribly guilty about what sort of mother I must have been to my son. Often there was not enough food because I had spent all my money on drugs. Other times I did not go to Marley when he was crying.

Still living in the flat owned by my father, I saw less and less of my parents as my drug life took over. It was at this point that they decided to take action to stop Marley from being taken into care. I was just relieved that I did not have to worry about him any more.

My father stopped giving me money, but that didn't matter. It was no longer enough to keep up with my habit anyway. I then turned to selling my body. The first time was with a dealer who offered to take sex instead of money. I felt sick afterwards but the drugs made me feel better.

When I started, I could choose the men I went with, getting between £100 and £500 a time. I had quickly learned that 'new' girls on the street always got paid more. Sometimes I was paid as much as £1,000 - especially if the man took drugs himself.

At weekends, I went to my parents' house to see Marley. Mum kept asking me whether I was still taking drugs, but I wouldn't tell her. Then one day she asked me if I had ever taken money for sex, and I said: 'Yes.'Mum ran out of the room.

When I began injecting drugs, aged 28, my father decided enough was enough and that 'tough love' might be a better approach. He asked me to leave the flat I was living in, which belonged to him.

I did so, and found a place to sleep in a shelter for the homeless. Over the next 18 months I slept in squats or homeless shelters. I was physically very weak, having lost more than one-and-a-half stone.

And I'd become the victim of frequent violent attacks, sometimes by men who paid for sex; at other times, by homeless people who stole the money I'd got for it.

A few weeks after I'd been kicked out and realising how hard my life was, my mother begged me to come home so that my parents could look after me.

I did once, and was clean for ten days, but I felt so ill - shaking, crying and suffering from the most horrible paranoia - that I went back on the streets.

Two months later, I was raped. I didn't report it to the police. I felt I didn't deserve to be helped after the way I'd behaved. I wanted to get home to Mum and Dad.

I wondered whether my parents would even allow me in the door. I rang the bell feeling so fragile I could hardly stand.

Mum took me in her arms and hugged me. She helped me lie down on the sofa and covered me with a blanket. After that I must have lost consciousness.

Hours later I woke to see my mother talking to someone on the telephone. She told me that she and my father were going to take me to the Promis Recovery Centre in Kent that evening. I was too exhausted to protest.

Arriving at the treatment centre, I found all the staff and patients so welcoming that I was simply relieved to find myself somewhere warm, dry and comfortable. For the following nine weeks I was given rest, food and therapy.

Coming off heroin was very hard. Detoxing my body was tough; I suffered sweats, shaking and nausea. But the emotional and psychological battle to get clean was even more difficult.

I had to find something to replace the role that heroin had played in my life for so many years. I was determined to try - not only for my own future, but for Marley, too.

Mum and Dad visited every couple of weeks, often bringing my son. He was still very affectionate with me, but also bewildered.

Family therapy sessions with my parents were probably the hardest. I knew I had to be honest, yet I was so ashamed of my behaviour. But finding myself among other addicts and seeing that they were beginning to get their lives back on track gave me hope.

I realised that I must take responsibility for my addiction and that it was within my power to lead a fulfilling life without drugs.

Four months on, I have remained clean and am now living in London. I plan to get myself a flat and a job so that I can at last become a proper mother to my son. Yet I am only too aware of the gratitude I owe my parents. My treatment cost them £50,000.

My father says that I have already had my inheritance. But he did more than rescue me from drugs.

He saved my life. Once I have found somewhere to live, and my parents are certain that I can be trusted to take care of my son, we have agreed that I will have Marley again.

I will do everything in my power to make sure that happens soon. I have already missed too much of his childhood.

For more information about Promis addiction treatment centres, see www.promis.co.uk or call 01304 841700.