After delivering striking performances in The Prestige, I'm Not There, Rescue Dawn and 3:10 To Yuma, Christian Bale once again dons the cape and the cowl to play embittered vigilante Batman, and his alter ego, multi-millionaire Bruce Wayne, in The Dark Knight.

Having removed his Batsuit for the day, his hair still damp from showering off sweat and latex, Christian Bale slips into another, far more impenetrable suit on the Chicago set of The Dark Knight, the sequel to the highly acclaimed Batman Begins. This is the invisible armour that he wears to protect himself from the real world, a place where the villains aren't as evident as those that roam the streets of Gotham City. For Bale, the only enemies are those who seek to unveil his true identity, believing that his dramatic work is best served by preserving his anonymity. "An actor should never be larger than the film that he's in," he famously stated twelve years ago.

True to his word, Christian Bale continues to slip under the radar despite a prolific career which began, aged thirteen, when he was cast in the lead role of Steven Spielberg's Empire Of The Sun. Going on to earn respect with Velvet Goldmine, American Psycho, The Prestige and 3:10 To Yuma, career mistakes like The Secret Agent, Shaft and Reign Of Fire were quickly erased. "Look," he says today, somewhat flustered. "I'm an actor, not a baby-kissing politician. I kick myself whenever I reveal too much about myself. I don't view my personal life as a gimmick to be used to promote a film."

Having lost an alarming sixty pounds to play a troubled insomniac in 2005's The Machinist, Bale bulked up for Batman Begins, before returning to his usual lanky body type. Buffing up again for The Dark Knight last year, he remains formidably fit. Wed eight years to former model and make-up artist Sibi Blazic, the 34-year-old actor's intensive approach to his work has softened little, even in the three years since the arrival of the couple's daughter, Emmaline. Even the most hardened thespians undergo an attitude adjustment in the aftermath of parenthood. And while his little girl may bring some perspective to his seriousness as she plays with her father's action figure, for Bale it's all business.

Refusing to acknowledge the ludicrous nature of playing a man who dresses up as a bat, Bale scowls, "You have to take a leap of faith and just really do what you believe to be right," he says. "But a man dressing up as a bat is silly, so the only way to play it is like he's a demon himself. That's what I never really got from the other Batman films, and so it was clear. I didn't want to play it any other way. So when you can tread this line where you can actually be a man dressed as a bat, and not have it be absolutely silly, it's fantastic. We've created this weird world where you can actually believe that this man genuinely believes that dressing up as a bat is the best way to combat crime - and it actually ends up working," says the Welsh-born actor, who has signed for three Batman flicks.

Batman Begins earned US$372 million at the worldwide box office following its 2005 release. And despite the fact that two years earlier Bale's career was on such shaky ground that his house was repossessed, today he spares any false modesty. "I'm very proud of what we did with the first one," Bale says. "I was never really a fan of the previous Batman movies. I like working with Chris [director Nolan], and - not to sound too full of ourselves - I think we did a good job with the first one, and we've done an even better job with the second one."

If it seems like Bale is finally enjoying himself, then he refuses to be seduced by the easy life of your average Hollywood leading man. Just don't suggest that he prefers challenging roles. "I still enjoy working in a variety of movies," he explains. "The term 'challenging' tends to refer to when you're working with idiots and it's not going well. Then you're faced with the challenge of, 'Right. How do you try to make this work?' I like to think that I can recognise those situations before going in, although I've certainly made errors in the past. But when I'm working with good people, I pay little regard to the amount of effort required. I actually like having to put in a lot of effort, so I don't consider that to be a challenge. If there are good people around you, no role is too difficult."

Ask if his new status as superhero and highly paid Hollywood star has earned him more respect at home, and Bale grimaces. "Maybe I live in denial but I like to think that I get a fair amount of respect the whole time. But I'm unsure about the level of respect that you can acquire when you go to work in a rubber suit, you know? It depends on how you look at it."

And depending on how you look at it, Bale may well be the most talented actor alive who can proudly say that he's not a celebrity. "I'll take 'cult actor' over 'celebrity' any day," he concedes. "That's absolutely fine by me."

The Dark Knight is released on July 16.