Nicholas Conn had the perfect life path ahead of him – he’d had a happy childhood, a Watford Boys’ Grammar School education, and now he was embarking on a career as a police officer in the Met.

He was 19 when he joined and had just passed his medical test – and his cousin, also in the force, gave him a line of cocaine to celebrate.

“It was just supposed to be a celebratory thing,” remembers Nicholas, from Borehamwood. “I felt euphoric, it was like all my insecurities had just gone. The minute I took it, it was, like, this is what I’ve been searching for, this is how I’m supposed to feel.

Nicholas chased that feeling for the five years he was in the Metropolitan Police Service and for a number of years after he left, and his habit dragged him down into a life of drug running and trafficking, and left him penniless, homeless, beaten and wanted by the Albanian mafia.

Clean for five years now, Nicholas has dedicated his life to making amends and helping other addicts – he has set up Help 4 Addiction and just published a book, The Thin White Line, about his experiences.

“It was really hard to write,” says Nicholas, 31, who enlisted the help of a ghost writer for the book.

“We worked on it for two years and it brought up a lot of sore memories. But I want to try and give people hope and let them know that it’s not just your typical ‘scummy druggie’- I’ve used with multi-millionnaires, people from all walks of life.”

Nicholas grew up in Radlett, Carpenders Park and Bushey, and stayed in Hendon while he was training for the Met.

“I lived quite a straight life while I was in the police, although I was using all the time,” he says. “I was nicking all these druggies and thinking ‘You’re scum’, but I completely didn’t associate it with what I was doing myself. I was in so much denial.”

One of the symptoms cocaine users experience is extreme paranoia – something only heightened by working in the police.

“I was a response driver and using not far off 8kg a day,” says Nicholas. “One day a call came over that a colleague had been attacked and I had to drop everything – but I was doing a line of cocaine in the toilets. I ran and got in the car, lights on, but then realised I’d left my credit card, rolled-up note and line of coke on the toilet. So I had to turn the car round. I got back and grabbed all my stuff just as my sergeant was about to go in to that cubicle.”

Nicholas had to leave the force after about five years (he won’t go into why, but covers it in the book) and “this other life just sort of happened”. He worked for a number of estate agents in Borehamwood, Radlett and St John’s Wood. But his cocaine habit – he had dealers in Watford and Borehamwood - got him into so much debt that he took a job with a property investment specialist who sent him to Berlin.

“I found out they were Albanians and they owned a club over there,” he says. “They gave me a bit of gear and I was drug running and running women from one brothel to another.

“But all that gear they’d given me, I found out it wasn’t a ‘thank you very much’ but was actually building up on a tab and I ended up owing them 40,000 Euros.”

Nicholas ran from East Berlin to West Berlin and, having no money, was left homeless for a few weeks.

“You look back and think ‘What the hell?’ I came from a good background, a loving family, I had a good education – how did this happen? And the answer is addiction.”

Nicholas’ turning point came when he had returned to the UK and was doing security at a nightclub in Hertfordshire five years ago.

“I was patrolling and saw this guy in a dark room at the back, on the floor, fitting on the drug GHB.

“I robbed him. I took his wallet, all his money, and his cocaine while he was fitting, rather than calling for assistance or an ambulance. I went into the toilet and used the line of cocaine. Then I looked up at myself in the mirror and thought ‘I don’t want this anymore’.”

Nicholas is upset recounting this but believes honesty is important if he is to help other addicts. Through his company, he now lets them know what options they have and what type of treatment would best suit them – and by inspiring them with his own example.

“I’m really lucky that I managed to find the right help, but a lot of people don’t know what to do, where to go, and they’re scared.

“It’s not easy to pick up that phone. People think ‘I’m a doctor’ or ‘I’m a lawyer, I can’t make that call’. But it doesn’t matter what profession you are. When they hear I was a police officer, I hope I can give them some inspiration and some hope.”

  • The Thin White Line is available to buy or download for your Kindle at Details: 0845 459 4357,