He was a little kid in Luton when James Bond first came into his life; today David Arnold is the composer who knows the score when it comes to looking after the secret agent. He tells Andrew Mueller how Daniel Craig inspired him to overcome moments of 'blind terror'

Someone once wanted to do a documentary about me scoring a film," says David Arnold. "I said they'd get a great 10-minute programme. First, you get the phone call. Then, you go to a meeting. Then you sit for three months with your head in your hands."

Casino Royale is Arnold's fourth Bond score (the theme song from Casino Royale, "You Know My Name", was co-written by Arnold and its vocalist, former Soundgarden and current Audioslave frontman, Chris Cornell).

The 44-year-old British composer joined the franchise on 1997's Tomorrow Never Dies. It was, as he recalls, the keeping of what he'd long thought of as a date with destiny.

In his eyrie in Air studios, a renovated church in north London, Arnold still recalls, with endearingly undiminished wonder, his first exposure to Bond. He was eight, and attending a birthday party at a British Legion club in his native Luton.

"Which, obviously, is about as far from Bond's world as you can get," he says. "But someone brought in a projector, and a tape of You Only Live Twice...and how can anybody not want a taste of that?" Arnold was, and remains, transfixed by the score John Barry composed for You Only Live Twice, and 10 other Bond films.

"The music," says Arnold, "was elegant, with an odd melancholy, as well as great excitement and great swagger. But Barry created a genre which hadn't existed before, exotic and alluring and so gloriously ignorant of everything else that was happening in popular music. Goldfinger and Diamonds Are Forever were written post-Beatles, but they were able to exist in this James Bond universe, beyond anyone else's rules."

Arnold's opportunity to match his own talents against Barry's legacy followed his scores for Stargate and Independence Day (which earnt him a Grammy), and his curatorship of an album called Shaken & Stirred, on which hits from the Bond canon were covered by Pulp, Iggy Pop and Propellerheads, among others. When the call finally came, though, it evoked the mixed feelings that always accompany the opportunity to finally live out one's dreams. "A moment of great elation," confirms Arnold, "swiftly followed by blind terror. All of a sudden, it's not talking about it, and thinking about it, it's doing it, and that's when the historic nature of it starts looming over your shoulder, and nothing you can do is good enough. Whoever does the music is forever in the shadow of John Barry, just like whoever plays Bond is forever in the shadow of Sean Connery. And it's almost impossible to do better." There is, certainly, no other cinema phenomenon remotely comparable, no other character in whom so many succeeding generations have an emotional investment. "That's true," agrees Arnold, "but that's why it's exciting. For at least the first three seconds, as that white dot moves across the screen, everyone in the cinema is willing it to be the best Bond ever."

That emotional investment, acknowledges Arnold, can also be intimidating.

"But," he says, "you have to find a way of abandoning your concerns. On this one, I was really inspired by the way Daniel [Craig] did it - he just played the role, without looking over his shoulder. With the Pierce Brosnan films, I perhaps looked over my shoulder a little too much. This time, I think was more looking left and right. I mean, some of it obviously owes a debt to John Barry, but I'm not sure Bond could stand that much reconstruction - if the things aren't there that make it a Bond film, it stops being a Bond film."

Arnold also understands that his work on Bond rather drowns out his other work - which has included scores for Little Britain, Shaft, Godzilla, The Stepford Wives and 2 Fast 2 Furious. He nevertheless discusses past Bond films with the unreconstructed ardour of a fan. He believes that we are overdue another villain plotting from inside a hollowed-out volcano ("With a monorail, obviously"), and talks about Bond films still to come, undaunted by the punishing creative schedule involved. The logistics of putting the films together require him to compose two or three minutes of music a day, something which can consume 18 or 19 hours of that day.

"It's always at the back of your mind," he says, "like knowing that you have to climb Everest next year. But there's nothing else like it. I've just done music for Amazing Grace, a film about William Wilberforce which is out in January. It took about an hour to write two minutes of music for that. It came incredibly easy. It was simple, and gentle, just people talking, no machine guns or car chases. One minute of people sitting and talking about slavery in the House of Commons is a very different proposition from running at a hundred miles an hour escaping from tanks and helicopters."