In 1983 they had claimed the mantle of The Beatles by playing New York's Shea Stadium.

But as all three freely admit, their years as rock stars were also years of bitter conflict, sometimes to the point of fistfights backstage. "We would be playing arenas and feeling the love pour on to us," Stewart Copeland says. "And then you would come backstage, to the guys who mattered most, and feel the unlove." From the beginning they had been three disparate personalities. Copeland voluble and extroverted, Sting earnest and pensive, and Andy Summers happiest talking about chord changes and guitar gizmos. What connected them was the music - and that was what they fought over hardest of all.

I meet them in a recording studio in Vancouver, where they are rehearsing for a very public first gig: opening the Grammy Awards broadcast with their 1978 hit 'Roxanne', before announcing a world tour the next day. They are working their way through a list of two dozen songs: Sting, 55, on bass and vocals; Summers, 64, on guitar; and Copeland, 54, on drums. For the first time in decades, The Police will be back together for more than one night. "I've trapped myself back 30 years," Sting says.

The old Police sound had a lean, nimble, pointillistic approach that Summers called "the sound of tension", and that tension sounds intact as the band kick into 'Message In A Bottle', with its jumpy guitar riff and stamping beat. Half a minute later, Sting waves the song to a stop. "Pick," he says tersely, his voice slightly irritated. "It doesn't work."

Summers has been playing guitar with a pick, not his fingers as he used to. "You thought for a second that he wouldn't notice?" Copeland cackles. Summers shrugs: "I played it with a pick yesterday, and he didn't say a word." He abandons the pick, Copeland shouts "One! Two! Three! Four!" and in an instant the song is galloping forward again. It's just another moment of readjustment for the three headstrong musicians rebuilding a tricky alliance.

"We didn't go to school together," Sting says. "We didn't grow up in the same neighbourhood. We were never a tribe. There was friction for the right reasons. We care passionately about the music and we're all strong characters, and nobody would be pushed around. So it was part of our dynamic. We fought like cat and dog over everything."

Since they last worked together, all three had become used to being bandleaders and composers. "It would be much easier just to go into the studio and make a record with my band," Sting says. "And it's not just the music. It's the social stuff, it's the personal psychology stuff of going back to a marriage - returning to a dysfunctional marriage and making it better. I really want it to work."

The Police have already had a few days of rehearsal before allowing a visit from an outside observer, and they have built a wary, joshing camaraderie. Sting, who at first had tried to lead the reunited Police by telling the others what to play, is still taking charge and picking songs to work on. But he is now prefacing his ideas with "I think...", "Perhaps..." and "Do you think we might...?" He and Summers tease Copeland about wearing a sweatband; in turn, Mr Copeland punctuates their discussions over abstruse chord substitutions with mock exasperation.

"We play the last show of the tour in 2008," Copeland says. "And I've got $10 here that says Sting will suggest another chord for Andy."

"And why not?" says Sting.

During a break, Summers says: "I feel it all coming back, the whole thing. Some of it's moronic, like wandering around being a rock star and everybody going, "What do you need, what do you need?" And I'm thinking, 'Oh yeah, I remember this'." But it's like getting into an old familiar suit. I feel all the old reflexes coming back."

They were the reflexes of virtuosos determined not to become their own tribute band. "At the moment it's an exercise in nostalgia, certainly," Sting says, "but also trying to get something modern and something new out of this situation. That may result in another song. I can't predict. I'd like that to happen. But we're just trying to remember the chords at the moment."

The sound The Police created in their seven years together - light-fingered but assertive, musicianly but unmistakeably pop - hasn't aged as fast as much 1980's music. "We were the greatest rock band in the world, and that's they way we want to be," Summers says. "And we still have enough ego to think that we can come back and blow every other band out of the water."

The Police know they will have to get along for a year to come. "I used to think that strife and struggle and tension were important in a band," Copeland says. "I no longer believe that. And, in fact, this band has been rescued by our refusal to fall into strife and confrontation.

"When we arrived here in Vancouver, we had big musical problems. And we didn't resolve them by shouting at each other, by getting angry at each other, by power plays, by any of that stuff. We resolved our musical differences by committee. We had to use our social bond to get through and try different solutions to the musical problems."

"There's more compromise now," says Sting. There's a sense of relax and it will be OK." He pauses. "So far."

© Source magazine (originally The New York Times News Service by Jon Pareles)