“The Scottishness comes through in my music,” says Doyle, 52, who is now based in London. “There’s a musical phrase in Harry Potter before one of the challenges that’s very like a Scottish snap — it’s an octave leap thing. You can often put a geographical label on a composer. I’m very proud of my heritage and you can hear from my accent that I haven’t gone transatlantic.”

He’s right, though if his accent had mellowed, you wouldn’t blame him. His success in the movie industry since his debut in 1989 with Kenneth Branagh’s Henry V through films such as Bridget Jones’s Diary, Gosford Park, Calendar Girls and Nanny McPhee means he leads a jet-setting lifestyle. As well as his London home, he has houses in LA and France — not least because of his repeated collaborations with the French director Régis Wargnier on films such as Indochine with Catherine Deneuve and, most recently, Man to Man with Joseph Fiennes and Kristin Scott Thomas.

“Someone said to me, ‘Don’t you find it frustrating writing music?’ I said, ‘No,’” he laughs. “It’s hugely satisfying. It allows me to travel the world, it pays very well, it’s given me incredible opportunities — what more do you want?” Somehow, between the composing, recording and nation-hopping, he finds time to keep up with his own young family and his parents, who live in Scotland — not to mention his 12 brothers and sisters.

No doubt many of them will be at the head of the queue for Harry Potter and the Goblet of Fire, in which Daniel Radcliffe’s boy wizard is joined by Ralph Fiennes, Miranda Richardson, David Tennant and the Scottish newcomer Katie Leung for a dangerous battle against Lord Voldemort and his Death Eaters.

“I’m particularly proud of my score for Harry Potter because it’s the biggest commercial picture I’ve ever done,” says Doyle. “It’s an enormously high-profile project and the pressure is substantial. I’ve done enough now to be confident I could pull something out of the bag, otherwise I wouldn’t have taken on the job. It’s been hard work but hugely enjoyable and it’s made me a bit of god among my kids.”

The complexity and maturity of Rowling’s book, with its new characters and dark themes, provided Doyle with a challenge to relish. “I’ve never written so many different themes, waltzes, dances and motifs,” he says. “It’s been a great opportunity to explore new ideas.”

He’s not been so rash as to drop Williams’ famous Hedwig’s Theme, which set the mood for the first three films, but neither has he denied himself his own musical vision — Scottish reels and all. “John Williams is a fantastic talent and following him was an enormous challenge,” he says. “We’re all very grateful to him because, up until Star Wars, film scores with a symphony orchestra were in the doldrums. Star Wars opened up a new generation of producers and directors to the power of the symphony orchestra sounds.”

The composer’s skill, he argues, is as much about knowing when to keep quiet as when to use the full force of the orchestra. “The art is to choose your moments. There was one scene in Harry Potter that stood up very strongly because the plot was so great. The temptation to add music had to be avoided.”

Being adept at musical scores is something he attributes to his background in Glasgow. A classically trained musician, he studied at the Royal Scottish Academy of Music and Drama. This was in the early 1970s, when the Citizens’ theatre was at the height of its international fame and Doyle found himself drawn to its flamboyant style. “The Citz was at the forefront of fresh new theatre and I was there during the golden years,” he says. “It was an enormous influence in my life.”

For years he worked as an actor, joining Branagh’s Renaissance company, a connection that would land him his first composing job on Henry V, for which he won the Ivor Novello award for best film theme. “It was overwhelming to have the City of Birmingham Symphony Orchestra, Simon Rattle conducting and my dad and my sister singing in the choir,” he recalls. “The album sells more now than it did when it first came out. It’s very gratifying.”

He also acted in Chariots of Fire, Much Ado About Nothing and has a small part in Branagh’s forthcoming As You Like It. The result is a feeling for dramatic structure that he believes puts him at an advantage. “Mike Newell, the director of Harry Potter, was keen that I should work on the movie because of my drama experience,” he says. “Scores are character-driven and, having been a performer, I find it easier. It’s not a prerequisite — I mean, Verdi wasn ’t an actor — but it helps.”

As well as the Shakespeare, he’s about to set to work on his first science fiction film, Eragon, starring Robert Carlyle and John Malkovich. After the fantasy of Harry Potter, he’s looking forward to broadening his musical palate still further.

“It’s incredible what a memory bank the musical side of the brain is,” he says. “You don’t consciously listen, but you’re open to everything — on the radio, in shops, there’s no escape from music pollution. My son said to me, ‘Dad, do you hear tunes in your head all the time?’ The truth is that I can’t sit still without hearing a tune.”

Harry Potter and the Goblet of Fire opens on Nov 18

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