Anthony Horowitz is a prolific writer for British television, involved in both the “Midsomer Murders” and “Foyle’s War” television series and many Agatha Christie TV adaptations, but he’s also the author of the Alex Rider books, a series of adventure stories about a fourteen-year old boy who becomes an agent in the British intelligence service that has captured the imagination of scores of young readers. Now the first of the books, “Stormbreaker,” has been made into a film titled “Alex Rider: Operation Stormbreaker,” written by Horowitz himself. It’s about Alex’s first undercover mission–to foil a plot of the evil computer magnate who’d killed his uncle.

When asked during a recent Dallas interview whether he’d always wanted to adapt the book for the screen, Horowitz immediately said, “Quite the opposite! My first instinct was not to write the screenplay. In fact, I tried to talk myself out of doing it, because I was very fond of the book, and I was nervous about making the necessary changes to turn it into a screen adaptation. I also thought that somebody else might bring a fresh pair of eyes to it–new, better ideas than I might have. But [the producers] were very keen to have me in the loop–perhaps they recognized that the fans know me, and I would reassure them. But I’m quite glad that I did decide to do it, because it was a fun process.”

Horowitz was surprised when a host of big names became attached to the project–among those appearing in the film are Ewan McGregor, Mickey Rourke, Bill Nighy, Sophie Okonedo, Alicia Silverstone, Missi Pyle, Robbie Coltrane and Stephen Fry. “I couldn’t believe the quantity and the number of big names that they’ve gotten in the movie, some in very small parts. To this day I don’t quite know how it happened–everyone just wanted to be in it.”

But the most important role was that of young Rider, and Horowitz had a hand in choosing Alex Pettyfer, a fifteen-year old model-turned-actor who also came to Dallas. “What happened,” Horowitz explained, “was that I was the first person to see him. I was watching a show called ‘Tom Brown’s Schooldays,’ which was a big Christmas special. And when Alex came on the screen, I called to my family and said, ‘That’s Alex Rider.’ He played Tom Brown in that TV movie. And I rang the producers next day and said, ‘Look, you’ve got to see this kid.’ And they did. Of course, they also saw five or six hundred other kids. By and large I was kept in the loop, but I can’t say that I had control of the casting of anybody.”

Pettyfer said that “Tom Brown’s Schooldays” was his first major film, after his modeling career and “one or two commercials. I auditioned for it, and away it went. These are the only two [films] I’ve ever done.”

He described playing the young agent as a “very exhausting physical and emotional experience,” but an enjoyable one, especially since he did all his own stunts–“the bike thing, in the tank, in the water, on the helicopter. And I loved doing the fight scene.” He added, “I read ‘Stormbreaker’ and ‘Point Blank’ [the second Alex Rider book], and I thought they were fantastic, and I thought the adaptation from book to screen was great.”

Pettyfer explained his character’s popularity by saying, “People can relate to him. You can step out of the cinema and believe that one day you can step into his shoes. He can’t sling webs out of his hands, or fly. He’s a normal child, and he’s finding himself, and you go on an adventure with him. You connect with the character.”

In fact, that connection was the one thing that gave him pause about the role. “The only thing I was nervous about was how [I would] portray the character,” he said. “If you don’t portray him properly, you’re going to let a lot of kids down who have thought about this character from the books by themselves, created the character by visualizing him.” That’s why he was so pleased when youngsters have come out of the movie and said that from now on, when they think of Alex Rider, it will be Pettyfer they see in their minds.

“That’s a good feeling,” Pettyfer said.