Cannabis

"My son James was always a popular teenager. He had masses of friends, was good at sport, and was also intelligent and handsome. Like many boys in their teens, he was constantly going out to meet friends, arrange football or cricket games or see his long-term girlfriend.

He'd done well at school with 10 GCSEs and three A-levels, and he went off to Southampton University to study history and politics. He was following the fine example of his sister Joanne, who had been to Nottingham University and was doing well in public relations.

I remember thinking one sunny day seven years ago that life was good, and couldn't get much better. I had a good job as a journalist, a great wife, and two lovely children. I was proud of both of my kids and thought they had a great future ahead of them.

But I hadn't reckoned on cannabis."

One father's cautionary tale ...