The second factor was Joe's illness. Stuart had written about a third of the book when his son was diagnosed with a rare form of cancer. Joe died at the age of five after a two-year illness. The War Zone was completed while Joe was dying, and this, says Stuart, made his writing reckless, as he worked in snatches between his son's chemotherapy sessions. "It's the only time in my life that writing came fast. I didn't want to waste any time. I would race back to the flat while Joe was sleeping for a few hours. It somehow made me fearless; whatever flaws the book may have, it was written with a real commitment to being as honest as possible. I wanted to push it as far as I could. It scared the hell out of me. When I wrote the ending, that wasn't how I had planned to resolve the book - the end almost wrote itself. It was weird."
As the book progressed, Stuart began to find the topic increasingly fascinating and abhorrent at the same time. "I find it so hard to understand how parents can abuse their children. One of the great joys of parenthood is holding your child's hand and exploring the world with them; how you can bring a child into the world and go from that to fondling your child sexually and abusing them is beyond me. I can understand to some degree how physical abuse might happen, how someone might hit out, though that doesn't excuse it, but sexual abuse is something else."
The War Zone, reissued on 9 September to coincide with the release of Tim Roth's film of the book, was controversial from the start. Set one long, hot summer in Devon, the book is written from the point of view of Tom, a teenager who discovers that his sister Jessie is having a sexual relationship with their father. Tom's anguish and despair as he realises the deceit and ugliness that lie beneath his family's outwardly respectable middle-class facade drive him to desperation; the family pulls itself apart. In 1989, when it was first published, the book won the Whitbread Award - but was then withdrawn because one of the jurors found it so "repellent" that she complained to the organisers.
The film remains true to the book in its uncompromising portrayal of a bleak subject. Tim Roth took the unusual step of asking Stuart to write the screenplay of his own book. "It's very rare that happens," says Stuart. "Tim never actually told me this, but he has written that he was quite prepared to replace me as writer if it didn't work out. One of the problems is that authors can be very precious about their own work. We stripped The War Zone right down to the essentials - I've always felt films should be different from books, you should take the essence of the book and work with that." A classic example, he says, is Apocalypse Now and Heart of Darkness.
Also, Stuart admires directors like Robert Altman who encourage improvisation, which is unusual for a writer. "When I write dialogue, I'm not particularly concerned that the exact dialogue is spoken; if someone is more comfortable saying something that has the same sense or even a different sense, that's fine," he says. "Not all writers feel that way. But the book is there - if people want to read my book they can read my book, but I want the film to work as a film." And work it does. Reviews from the Sundance, Cannes and Edinburgh film festivals are talking in terms of a tour de force, while the American distributors are hoping for Golden Globe and Oscar nominations.
However, despite this success, adapting his novel has been a very difficult process for Stuart. The emotions invested in the book are still raw, 10 years later. After his son's death and the subsequent breakdown of his relationship with Joe's mother, he went into a prolonged period of therapy; he has had to go back to therapy to deal with the feelings thrown up by the making of the film.
"This summer has been particularly hard," he says. "I have been as depressed or even more depressed as I was when my son died. The film has become increasingly difficult for me to watch." The film carries a dedication to Joe. "When the producers asked me if they could do this, if it was okay with me, I cried so hard I had to put the phone down and call back later. We used to take Joe to Devon quite often. I love Devon, and watching it, the memories that come back are just too painful. It's 10 years since he died, and the anniversary has just crept up on me. You think you've dealt with things but find you haven't."
Though he has been congratulated by victims of abuse on the accuracy of The War Zone, Stuart is adamant that the book is not based on personal experience. "I wasn't abused by my parents. I love them. The book has always been very hard for my parents to deal with. I don't think I fully realised when I was writing it how hard it would be for them, that people might think 'Oh, he obviously went through it'." The book is left deliberately opaque in parts; Stuart wanted to leave unanswered questions. "I didn't want to explain everything. I wanted it to be so you could read it and think 'Oh god, that could be my family', rather than 'This kind of thing happens on a council estate somewhere else and it's not to do with my life'."
When The War Zone was first published, one reviewer called it "The Catcher in the Rye of the Nineties". It is, agrees Stuart, also about the pain of adolescence - a more accessible theme than incest. "It's about all the complexities of that time of your life, and the way that the family is the place where we learn about the world. Writing from Tom's point of view, exploring the pain of exclusion he feels, hopefully is something everyone can relate to. All of us have experience of exclusion."
Despite all the accolades and critical acclaim, and the renewed interest in his novel, Stuart is looking forward to life getting back to normal. He hopes one day to have another child. "I was never a baby person, but when my son was born I was instantly besotted. Now I look at children and babies and think 'That child is so beautiful' - I love the joy on children's faces, the openness to the world." He moved to the US shortly after Joe's death and his home these days is Los Angeles, where he lives with his artist wife. "There is a part of me that will be really happy when all of this is over," he says. "Kissing goodbye to The War Zone will be quite healthy for me, I think."
'The War Zone' by Alexander Stuart (Black Swan pounds 6.99) is reissued on 9 September, when the film will be on general releaseReuse content