HE may look like the epitome of the Hollywood success story, but actor Matt Damon hasn't exactly led a charmed life in Tinseltown.

Like his boyhood best friend Ben Affleck, the 33-year-old New Englander knows what it's like to fall from grace.

It's not so long since he and Affleck were riding high as the new wunderkinds on the block. Then, a couple of years ago, after Matt's films All The Pretty Horses and The Legend Of Bagger Vance bombed at the box-office, his career was suddenly in trouble.

"You can look at me and think, 'This guy has it all', but let me tell you, I don't think anyone in this business ever feels secure," he admits.

"After those two films I didn't have a movie offer for an entire year."

Instead the boyish-looking American found solace on the London stage, after playing the role of a memory-challenged assassin in the thriller The Bourne Identity.

Early fears that the thriller would bomb too were ill-founded - its surprise success was just the shot in the arm Matt's career needed.

Now he's back as the former superspy in the sequel The Bourne Supremacy, opening today. This time, with his memory more or less back, the question driving the fast pace isn't 'Who am I?' but 'What did I do?'.

German star Franka Potente reprises her role as Bourne's love interest and pillar of support as the action switches from India to Europe and America in quicksilver cuts by British director Paul Greengrass. The critics have had high praise for Matt's depiction of the haunted assassin coming to terms with his past. This time Jason realises he has committed horrible deeds he needs to atone for.

Matt knows that being cast as sinister secret operative Jason Bourne wasn't an obvious move, given his boyish all-American looks.

"I look so young, and this guy clearly has got a very dark past and people don't look at me and necessarily think that," he admits.

"I just tried to look at every different aspect of trying to make this guy as believable as possible."

The two Bourne films are a departure from the usual good guy generic secret agent films, and the complexity of Jason's character appealed to Matt.

"I like the fact that this character is deeply flawed in some ways, that he has this dark past and is trying to come to terms with the things he has done."

Known for being a workaholic, Matt went to great lengths to prepare himself for the role. He also does some of his own stunt work, including an exhilarating car chase through Moscow.

"The theory we applied was that it's really important to have me doing it because audiences are smart enough to know, when you cut to the wide shot of the really buff stunt man doing it, it's a give-away," says Matt.

With his stardom in full bloom again, Matt follows the Bourne movie with another sequel to a monster hit, Ocean's Twelve, which reunites the gang from Ocean's Eleven.

"George Clooney's home in Italy is one of the most beautiful places I've ever seen. Let's just say we had lots of fun there. Brad Pitt is pretty lethal with a super soaker squirt gun."

Matt also has a couple of interesting independent projects on the horizon. Terry Gilliam's Brothers Grimm is in post-production, and he's preparing for the political thriller Syriana.

Having risen from obscurity with Ben Affleck with their Oscar-winning film Good Will Hunting in 1997, Matt quickly entered the fray as one of Hollywood's brightest young stars. But he says courting stardom was never his plan, nor was box-office appeal.

"I never really had a strategy. A lot of actors I know make decisions based on a strategy. They'll do a film because they think it's going to do very well at the box office, but so often for those big films, everybody gathers for that reason and nobody's passionate about it. So you end up with a mediocre, expensive juggernaut that dies on the vine."

Having experienced the career troughs as well as the peaks himself, Matt has sympathy for Ben Affleck, who became tabloid fodder for his celebrity-circus romance with Jennifer Lopez and their movie collaboration on the turkey Gigli.

"The misconception was that Ben was out there trying to drum up publicity for himself," says Matt. "Once you get caught in the crossfire of those tabloids, it really is the death knell of your movie career in the short term.

"Nobody who can see you in a magazine every day is going to pay to see you in a movie."

After his own highly-publicised romances with the likes of Winona Ryder and Minnie Driver, Matt's keeping his private life much more low-key now, and prefers not to talk about his latest flame, interior designer Luciana Barroso.

"I kind of operate under the assumption that it's all going to go away at some point," he says, "and I'm OK with that."

PROFILE

Real name: Matthew Paige Damon

Birthdate: October 8, 1970

Significant other: Luciana Barroso

Career high: Winning Best Original Screenplay Oscar for Good Will Hunting

Career Low: The Legend Of Bagger Vance

Famous for: Announcing break-up with Minnie Driver on Oprah Winfrey's TV show

Words of wisdom: "Mom comes from the school of thinking that all this is a tremendous amount of resources to be wasted on me. She's like, 'I know who you are'."