For a long time, Kay Smith thought of herself as two separate mothers. "By day I was the mummy of a sweet little girl, taking her to the park, baking cakes with her, reading her stories," she says. Everything changed once her daughter, Lydia, was in bed.
"As soon as she went to sleep I'd start worrying about Matthew, my teenager. Often I wouldn't have seen him all day – but I knew exactly what he was up to. He was taking drugs.
"I'd sit there, terrified about where he was and who he was with. One night I remember arming myself with a baseball bat and heading off into the night to search for him. After a day with Lydia, it felt surreal to be out there alone on the dark and dangerous streets – it was another world."
Things came to a head one night when Matthew returned to the family home in Manchester, and started smashing the place up. "My husband, Robert, could see the state he was in, and tried to keep him out of the house," says Kay (50). "But Matthew went berserk – he pushed his way in and he started destroying everything."
It was frightening, especially for Lydia, then eight.
"We'd managed to shield her from Matthew's drug-taking, so she'd never known her brother in this sort of state," says Kay. "This time Lydia saw everything. In fact, she was the person who called 999."
Later that day, after the police had taken Matthew away, Kay made the hardest decision of her life. "I decided my little girl had to come first. Lydia wasn't safe in her own home any more – she couldn't live a normal little girl's life with a drug-addict brother. And that's the moment I knew I was going to have to turn Matthew, who was 17, out of our family home."
A few days later, Kay drove Matthew and his things to a hostel across Manchester.
"It was the worst day of my life," she remembers. "Matthew kept crying and telling me how sorry he was.
"And he was my baby once, just like Lydia, so inside it was tearing me apart. But I had to stay firm. I knew some people would call me a bad mother for chucking my son out, but I also knew that, at some level, allowing him to stay was condoning his lifestyle. I also believed that before he could climb out of the terrible hole he'd dug himself into, he had to hit rock bottom.
"My big terror, of course, was that he wouldn't manage to do it and simply be found dead somewhere."
For Matthew, meanwhile, that day in 2010 is a blur.
"I was drugged-up and didn't really know what was happening or where I was going. All I did know was that I was having to leave home, and that definitely hurt."
Now 20, Matthew says his drug-taking started when he was 13. "I remember a lad at school skinning up cannabis in the music room, and then we smoked it in the field behind school."
That first time, he says, he didn't even inhale – "I just pretended to be high" – but he didn't need to pretend for long. "By 16, I was a total mess. I was hanging around with other drug-takers, jumping off the school bus each morning to go for a joint in the park. I was going to school late every day, taking ecstasy, cannabis and other drugs, and had basically lost interest in everything else in my life. I was on a slippery slope downhill, and fast."
For Kay and Robert, it was deeply distressing. "We'd never had to deal with anything like this before and didn't know how to cope," says Kay.
"For Robert, who used to be in the army, it was especially difficult. He found it very difficult to accept that we couldn't control what was going on, that we were helpless.
"Meanwhile, Matthew was in a terrible state and I was worried sick. He was grey and thin, his skin was appalling, he was on a very short fuse the whole time and he was totally paranoid. It was an utterly vile situation, and made all the more difficult and poignant because alongside it, Robert and I were trying to bring up Lydia."
Matthew remembers how he felt after his mother left him at the hostel. "They gave me a key and I went to my room. I remember thinking, what happens now? I just sat there all night smoking fag after fag, trying to make sense of it."
Life at the hostel was tedious and restricted, compared to home.
"I had to go to meetings about my addiction, and I was only allowed out two nights a week. Of course I was still taking drugs, but it was all a lot more difficult."
Kay visited regularly. "I used to take him food, but I never gave him money. Sometimes I'd take him home to see his father and sister, but I'd never leave him alone for even a second because I knew he would steal stuff to sell so he could buy drugs."
Matthew recalls: "Mum would take me home and I'd be looking at everything in the house thinking, I could get a few quid for that."
More than a year after moving out Matthew had what he describes as an epiphany.
"I realised I'd had enough. I thought, I can't go on like this – it's no life. I was down and depressed the whole time. I really missed my parents and Lydia and knew I had to work out how I could get back to them; how I could get out of this rut."
Kay says, "He sent me a text and it read: 'I'm not doing this any more'. He'd never said that before and I knew he meant it. It felt like a breakthrough."
It was – but breaking his drug habit wasn't easy.
"Wherever I went I could smell cannabis. I'd have a few beers to help me to cope and end up drinking myself into oblivion. Then I realised I'd have to stop the drink as well and that was really hard."
After 18 months, Kay decided Matthew could come home. But there were ground rules. "I bought drug-testing kits on eBay and said he'd have to agree to random tests. I told him he had to be helpful around the house, and be a responsible big brother."
Today life with the Smiths is very different. Matthew recently returned from Kosovo and has been working. "I've never seen such poverty," he says. "It has made me think about what I want to do with my life.
"I think more than anything I want to help people. I'd like to do youth work, maybe something to do with drugs counselling. I'm hoping to go to college and do a qualification in youth work."
Kay is proud of what Matthew has achieved. With tears in her eyes, she says, "It was so difficult to pull back from where he ended up: he had to be determined and strong to do it. Now he's an articulate, positive young man: he's got his life back. He's brilliant with Lydia, who's now 12, and she adores him. While I'd be lying if I said there weren't days when, in my worst nightmares, he goes back to drugs, I really do believe that's not going to happen."
Matthew says he owes everything to his mother.
"If she hadn't thrown me out, I'd be dead by now," he says. "I had no real awareness of how bad things were and was on a slippery slope that was going to end in disaster.
"What Mum did was tough love – really tough love. It took it out of her to do it. The only reason I survived this was because I had such a supportive family. I know how lucky I am."