Interview: Matt Damon - 'There's a style of acting that tends to get rewarded. It's not what I do'

• Picture: AFP

The last set-up of the morning calls for Damon, wearing a pork-pie hat, to burst out of a side door and hurtle down an alley that has been rigged with sprinklers. This is the start of the climactic chase, which takes his character, a political candidate, through downtown Manhattan. While this particular shot will amount to just a couple of seconds in the finished film, Damon is giving it the careful consideration befitting a thinking man's action hero.

Between takes, he walks over to a cluster of video monitors to watch playbacks and confer with George Nolfi, the film's director. Nolfi, whose writing credits include two of Damon's films, Ocean's Twelve and The Bourne Ultimatum, talks about the rhythm of the sequence and the music he is planning to use for it. They discuss the impact of the door smacking into the wall. Damon suggests ways he could orientate his body in relation to the camera. Details matter to Damon, who has put together his quietly impressive resume with a curatorial eye, working his way to the top of the Hollywood heap while avoiding the traps of a typical A-list career. "The leading-man stuff doesn't come easily to me," he says. "I've always felt like a character actor."

This may sound like false modesty from someone who, at 39, has yet to lose the golden-boy aura of his break-out role in Good Will Hunting (1997), a vehicle he wrote for himself with his boyhood friend, Ben Affleck. But the increasing variety of Damon's roles and the almost perversely self-effacing ease with which he sinks into them suggest the thoughtful, restless sensibility of an actor who, as frequent collaborator Steven Soderbergh put it, "is thinking about expanding himself as opposed to presenting himself as a movie star".

In Soderbergh's acerbic character study The Informant!, Damon transforms himself into a doughy, delusional executive who exposes an agribusiness price-fixing scheme. In Clint Eastwood's Invictus, he's a rugby captain entrusted by Nelson Mandela with bringing socially unifying sporting glory to post-apartheid South Africa. And he re-teams with Paul Greengrass, who directed him in The Bourne Supremacy and The Bourne Ultimatum, for Green Zone, in which he plays a chief warrant officer on a futile hunt for weapons of mass destruction in newly occupied Iraq.

Damon has made two films with Gus Van Sant, three with Paul Greengrass, five with Soderbergh (including all three Ocean's movies). He has also worked with Steven Spielberg, Martin Scorsese, Francis Ford Coppola, Terry Gilliam and Anthony Minghella. "I've learned a lot just by standing next to these great directors and watching them," Damon says.

He shared an Oscar for the screenplay of Good Will Hunting and wants to direct some day. (Affleck has already made the leap, to some acclaim, with Gone Baby Gone in 2007.) Until he finds the right project, he's happy to keep "arming myself with information," he said. "Clint didn't start until he was 39, and he's had 40 great years."

The hugely successful Bourne movies established Damon's athletic bona fides. It was Franka Potente, his love interest in the first two Bourne films, who taught him that "most people look ridiculous when they're running", he says. She told him to study videos of himself in motion. But what Damon does in the Bourne movies is trickier than just making an intense cardio workout look good. "It's the way he frames his physical choices as an actor," Greengrass says.

He singles out the foot chase through Berlin midway through The Bourne Supremacy that ends with Bourne jumping on a train. "The entire character hinged on that one dialogue-less moment," Greengrass says, in which Damon "had to convey three different ideas: first, he's evaded his pursuers; second, he feels a gnawing self-disgust because he's discovered he's a killer; and third, there's a huge implicit sense that he's got a plan."

For The Informant!, a very different kind of physical performance, he gained 30lb and had his face puffed up with prosthetics. The disguise obscures "the boundaries of the character", Damon says. "It was all a metaphor for this guy being kind of undefined."

That more or less sums up the quintessential Matt Damon role: the blank canvas hero. For him, the appeal of embodying such ambiguous characters is in peeling back their inscrutable facades. "As an actor you have to make decisions about what their motivations are," he says, "even if you don't let on."

Damon's method, discreet to the point of invisibility, is premised on not letting on, not making it seem like work.

Morgan Freeman, who plays Mandela in Invictus, says Damon is, "like myself, a journeyman", meaning it as a compliment. "There's no strain in his work." But understatement is often overlooked, as Damon knows. "There's a style of acting that tends to get rewarded," he says, adding: "It's not what I do." (His one acting Oscar nomination was for Good Will Hunting)

That has never stopped directors snapping him up, and Damon is solidly booked for much of the next year. After The Adjustment Bureau, he'll work with Eastwood on supernatural thriller Hereafter. He'll also be in the Coen brothers' adaptation of Charles Portis' novel True Grit; George Clooney's Hamdan vs Rumsfeld, about the US government's case against Osama bin Laden's driver; and Soderbergh's film about Liberace, with Michael Douglas as the kitschy pianist and Damon as his bodyguard and lover.

Damon says he is also becoming more comfortable using his celebrity to help causes he supports, though he has made sure to work on nonpartisan issues such as clean water for the world's poor through Water.org, a non-profit group he helped found. "I'm trying to get involved with something you can't really argue with," he says.

But he's also not afraid to show his political stripes.

Last autumn, he publicly expressed horror at the prospect of Sarah Palin "having the nuclear codes". And while both he and Greengrass were careful to characterise Green Zone as foremost a thriller, Damon seems more willing to discuss the film in political terms. "It's the original question of where were the WMDs," he says, adding the movie chronicles "the massive blunders that came at such a huge price".

Damon's overnight success made him a tempting target for a while, as in Team America: World Police, the animated satire in which the Matt Damon puppet is capable of uttering only his own name. But like all good post-modern celebrities, he also has offered himself up for self-mocking deflation (including a much-viewed mock music video in which Sarah Silverman sings about her torrid affair with Damon). Having fun with his own image is, of course, a savvier form of control. "You're not waiting around to get ambushed," he says.

Damon lives with his wife of four years, Luciana, and their three daughters in New York. "Barring me getting up on a bar and dancing or leaving my wife for Lindsay Lohan, there's no story to update," he says. "Every six months, someone comes and squeezes off a picture of me and, yup, I'm still married."

The Informant! is in cinemas from tomorrow. Invictus follows in February.