Children's favourite: The Anthony Horowitz story

This week, the author of 'Stormbreaker' has seven titles in the children's top 20. The movie version is making millions at the box office. But it wasn't always like this, as Louise Jury reports

He has been writing since the age of eight and his first novel was published when he was only 23 years old. More than a quarter of a century after he entered the profession, Anthony Horowitz, now 51, is finally garnering the kind of attention of which most authors dream but never achieve.

Hot on the heels of the cinematic release of Stormbreaker, the first film to star his teenage spy creation, Alex Rider, Horowitz's original novel has returned to the children's charts to knock Harry Potter off the top spot. The film, starring Ewan McGregor, Mickey Rourke and Stephen Fry, is currently the most popular British-made movie at the UK box office, while the Alex Rider novels take up seven of the top 20 positions in the children's book charts - the highest tally yet for their author.

It is a curious situation. An author who has enjoyed more than two decades in print is finally on the verge of becoming a household name thanks to his James Bond-inspired spy series which has sold nine million copies so far. Like Mark Haddon, who won the Whitbread Prize with The Curious Incident of the Dog in the Night-time after years of producing children's titles, Horowitz suddenly has a success story.

"It's very nice for him and it's certainly nice for us," said Henryk Wesolowski, sales and marketing director at Walker Books, Horowitz's publisher. "Anthony was an established author and his other books had done very well, but nothing of this magnitude. It was crunch time with Stormbreaker. He said, 'I've been writing for so many years and what I want is a biggie.'

"We read it and we liked it. But we didn't think it would go quite this ballistic. We went straight to paperback and it just seemed to take off. Every subsequent book increased sales by 50 or 100 per cent."

And that was before the movie. John Webb, children's fiction buyer for Waterstone's, said sales were up 100 per cent on a month ago and four or five times what they were a year ago - when interest in the sixth of the Alex Rider series was already high. "The film has really kick-started things. Like the Harry Potter movies or Narnia [based on The Lion, the Witch and the Wardrobe], the nice thing about the movie is it just drives more kids back to check out the original source material. The day the movie came out, it just went ape."

Once young readers have found Stormbreaker, they seem intent on working their way through the whole series, Mr Webb added. "It's unusual seeing so many books [in the children's charts] from the same author. Right now, our sales are through the roof."

If Horowitz was writing the story of his life, this could be the fairy-tale ending to a narrative that began, he has intimated, in the disturbing territory favoured by Roald Dahl or the Brothers Grimm. He was born in Stanmore, Middlesex, in 1956 into an affluent family where he was raised by nannies, and surrounded by servants and chauffeurs. His father, a wealthy businessman, was "a fixer" for the Labour Prime Minister Harold Wilson, according to family lore, though the precise nature of the fixing remains obscure.

Everything began to go wrong when, threatened with bankruptcy, Horowitz senior withdrew all his money from Swiss bank accounts in Zurich, deposited it under a false name and died soon afterwards. Despite his mother's efforts, the fortune was never found.

Nevertheless, Horowitz progressed through public school and won a place at York University before embarking on his writing career. His aim, he said, was "to make up for the shortcomings of my childhood".

Before inventing his super-spy teenage hero, he wrote TV crime series including Poirot and Murder in Mind and created Midsomer Murders and the war-time drama Foyle's War which his wife, Jill Green, produced. But it was with Alex Rider, which he dreamt up in 1998 and first published in the form of the Stormbreaker novel a year later, that he finally hit the big time.

They are derring-do action adventures with feats road-tested by Horowitz's elder son, Nicholas, who has tried everything from snowboarding to surfing to help out with the detail. Horowitz himself is an avid scuba diver who has travelled from the Andes to China to research his books. So far, he has produced six titles featuring Alex Rider, and a seventh is in the pipeline. A script of the second in the series, Point Blanc, is already in preparation as a follow-up to the first Alex Rider movie. As with the first, Horowitz is writing the screenplay himself.

What seems to excite him most about the movie is its potential impact on the book sales - and it is already clear the effect will be enormous. "There are whole areas of England where even after Harry Potter, reading is still something fairly alien. I would love to think that one of the results of the film might be that kids read the books," he said. But this terribly English writer - who refused all advances from Hollywood and gave the rights to British producers who promised to keep Rider as a British teenager in a London setting - also has an engagingly childlike delight in making it to the big screen.

Despite years of work in the related field of television, he admits that it was a very happy moment when he walked through the film set and spotted props that had been created to bring the product of his imagination to life. He is a cinema-lover - The Third Man is his favourite movie - and, as any other film buff can imagine, he revelled in the experience of the shoot. "On the set, I was a kid in a toyshop," he said.

Although the critical reaction to the movie was warm rather than ecstatic, it currently lies behind the American blockbusters such as Pirates of the Caribbean: Dead Man's Chest and Superman Returns at the box office. It is set to have taken £5m by the end of the week on an investment - principally from British investors including the UK Film Council - of £21.5m ($40m). It opens in Australia in September and the United States a month later.

Marc Samuelson, the producer, said they were "very pleased" with how it has fared so far. "So far, so good, it's very exciting," he said. "And the situation with the books is absolutely amazing - hilarious but great. We always knew that it would give a bit of a boost, but didn't know it would lead to that many books in the top 20."

What happens in future remains to be seen as the Rider novels have been written "in real time" with a fixed ending in sight. "I've always said that I will stop when Alex is 15 and he's 14 and nine months. The books have always taken place a few weeks or months apart from each other," Horowitz said.

John Webb of Waterstone's said it would be "absolutely sad" if the books do come to an end, though "if he has a nice ending worked out, it will be quite gratifying". He also believes there are other opportunities in store for a spy such as Alex Rider. "He could grow up and become an Andy McNab character," Mr Webb said. And McNab, a former SAS soldier turned thriller writer - whose own best-seller, Boy Soldier is currently at number 11 in the top 20 children's books - has certainly shown there is mileage in that.

This week's top 20 children's books

1 Stormbreaker (film tie-in version) Anthony Horowitz

2 Harry Potter and the Half-Blood Prince JK Rowling

3 Horrid Henry and the Football Fiend Francesca Simon

4 Love Lessons Jacqueline Wilson

5 ... Startled by His Furry Shorts! Louise Rennison

6 Kylie the Carnival Fairy Daisy Meadows

7 Flash Flood Chris Ryan

8 Point Blanc Anthony Horowitz

9 Stormbreaker Anthony Horowitz

10 Skeleton Key Anthony Horowitz

11 Boy Soldier McNab and Rigby

12 Clean Break Jacqueline Wilson

13 Pirates...The Book of the Film

14 Eagle Strike Anthony Horowitz

15 Candyfloss Jacqueline Wilson

16 Tide of Terror Justin Somper

17 Cars: The Magical Story... Pixar Movie

18 Scorpia Anthony Horowitz

19 Ark Angel Anthony Horowitz

20 The Amazing Story of Adolphus Tips Michael Morpurgo

List courtesy of Nielsen BookScan, published in The Bookseller