Of course, the first thing you want to talk to Stewart Copeland about is his time with the Police. So Stewart, what can you tell us? 'It was great.' Absolutely, it must have been. And what else? 'It was great.' Could you fill in a little detail? 'Fantastic. Wonderful years.' More detail? 'Really great.' Um, would you rather talk about Horse Opera? 'Yeah.' OK. These days, Copeland calls the shots.

Horse Opera, for which he composed the music, is due for transmission on Channel 4 early next year in a season of operas written for television. It's the story of George, a boring, bigoted clerk from Nottingham who spends his spare time running the local cowboy society and trying to write the Great Western Novel. During an argument with his Asian next-door neighbours he gets hit over the head with a cooking pan, and the rest of the opera is about what happens to him in his delirium. He finds himself in the Wild West, where a man without a gun ain't a man. Illusions are quickly shattered: Wyatt Earp - played by Rik Mayall - turns out to be a wimp with a taste for cosmetics; Copeland himself puts in an appearance as a murderous Jesse James. And while George temporarily becomes a hero, saving some simple townsfolk from a land-grabbing railroad baron, he finds himself drawn into a finale of Peckinpahesque violence, all slow motion and anatomically correct gunshot wounds. There is some messy plotting and some rather broad slapstick humour, but Copeland's twanging score keeps rattling along for the full 60 minutes.

It's his third opera - a surprise to those of us whose enduring memory is of a lanky guy with peroxide hair stuck behind a drum-kit while the one with the cheekbones and the high voice pogoed in the foreground. These days he's 41 and the hair is darker, but otherwise things haven't changed much. Post-Police he has stayed in the background, working away steadily, and highly successfully, as a composer. As well as the operas, his composing cv includes a ballet, a symphony, two entire seasons of The Equalizer and around 20 film scores, including Hollywood blockbusters like 9 1/2 Weeks, Wall Street, She's Having a Baby and three films by Ken Loach (Hidden Agenda, Riff Raff and his latest, Raining Stones).

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This second career began in 1983, while the first career was still in full flood, with Francis Ford Coppola's symbolist tale of delinquency and clocks, Rumble Fish. Coppola intended to score the film himself, but asked Copeland in to advise him on rhythm - a sensible move, given that some critics have rated Copeland as one of the best rock drummers in the world. In the end, Coppola didn't have time to write the music: 'And I, being an eager beaver, got in there and ended up doing it.'

More films followed and, more unexpectedly, so did a commission from the San Francisco Ballet - the company's director was fight director on Rumble Fish. King Lear duly appeared, scored for full orchestra, and, largely because of who Copeland is, created some stir in the media. During one interview somebody asked him, are you gonna write another ballet Mr Copeland, and he said, sure, when I've finished my opera. The next thing he knew, Cleveland Opera was on the phone expressing an interest. He told them he was joking and they said, fine but they weren't, so how about it?

He went out to educate himself in opera: he saw Strauss's Salome, and didn't much care for it. 'I went and saw a Birtwistle piece at the ENO and thought Jay-zuz Ker-rahst.' Finally, he discovered Wagner and loved it, and now he's a buff. But 'the important education for opera was not in the music that I studied but in The Equalizer. I did two years of 21 episodes a year, scoring a show every week. That's where you learn what the hell's going on, with film composing: the synergy between drama and music, and how the music interrelates with it, and how the music can drive it, change the subject, negate the information or amplify it.'

The first fruit was Holy Blood and Crescent Moon, a bombastic story of the Crusades, which was also a fairly blatant attack on Israel's involvement in Lebanon. Copeland spent much of his childhood in Beirut: 'The reasons for my strong feelings are because the town that I grew up in, in 1982 was raped by its neighbour in the south, just right there in front of everybody, raped. The napalm, the phosphorus bombs - do you know what a phosphorus bomb does? It's jelly, it sticks to the skin and does not go out. Children were being buried still burning.'

He's notably articulate, well-informed and passionate about politics, particularly Middle Eastern politics (although he points out himself that the situation has changed, and he can get down from this particular soapbox now). Perhaps that seems more striking because he is a rock musician (after all, would you ask Billy Idol for his views on European monetary union?), but it's also a reminder that he doesn't have a typical muso's background.

His father, Miles, was probably America's most public spy. During the Second World War, working for American counter-intelligence, he was responsible for stopping plots against Hitler (the reasoning being that with him out of the way, Germany might get somebody sane and competent to run the war). After a spell destabilising governments, he returned to the US at the end of the Forties to become a founding father of the CIA. In the mid-Sixties he was living in Beirut with his family, working as a political 'consultant' and greasing the wheel while apparently still acting unofficially for his old colleagues, shadowing Kim Philby, then Our Man in Beirut. The Philby kids were the same age as the young Copelands, and the two families were very close. Then Philby vanished, only to reappear in Moscow. The resulting publicity meant that Lebanon became too hot for Copeland Sr, and Stewart ended up in boarding- school in England.

These days, he's a confirmed Anglophile. He lives most of the year in LA, but every summer takes a house in England and spends a few months over here - he says it's the prospect of having weather that draws him. Having been in the Police, the British group that went out and conquered America, he finds himself regarded as an honorary Briton. 'It is a wonderful thing. It is the best kind of Briton to be, as a matter of fact. I move in all different areas of British society, and it is only possible as a foreigner.'

He has strong views on the stratification of British society - so rigid that people shouldn't even try to break out of it: 'They'll only develop anxiety and low self-esteem.'

Some of his ideas shaped Horse Opera, turning it into an American take on England. That wasn't how it worked originally. To begin with it was a play by Anne Caulfield, called Cowboys. Bob Baldwin, the director of Horse Opera, brought the play to Copeland when the idea of a television opera was first raised. 'I didn't really like the text that much, not because it was badly written or anything, but just because I didn't go for its basic premise, which is that the United States is 100 per cent evil and that 250 million people should pack their bags and re-emigrate back to Europe and give the land back to the Indians.' So, goodbye Anne Caulfield, hello rising young director / librettist Jonathan Moore.

As this tale suggests, Horse Opera is Copeland's show. In some of his other scores, working with what he calls 'symphonic music', he needed help with the orchestration. Here, he did everything but the singing by himself, in the studio. 'The style of the music is my own vernacular, it's my first language, so to speak - guitar, bass, drums.' There's also a banjo - actually a synthesiser, but convincing enough for Andy Summers to congratulate him on his playing when he heard the tape.

It's a far cry from his days with the Police, when he had an inferiority complex about being a drummer. In all seriousness, he suggests that playing the drums handicaps you in creative exchanges: when the others have an idea, they can pick it out on a guitar; the drummer has to borrow somebody else's, or just hum it. He quotes some rock 'n' roll humour: 'The joke about drummers is, the last thing the drummer said before he got fired from the group was, 'Hey guys, I gotta song]' ' These days, people listen.

(Photograph omitted)