For The Thin Red Line, Terrence Malick’s adaptation of James Jones’s novel about the battle of Guadalcanal, Brody survived months of tropical squalor in a simulated boot camp that included roaches, venomous spiders the size of dinner plates, and hostile Australian extras. After all that, most of his performance ended up on the cutting-room floor.

As a mohawked musician in Spike Lee’s Summer of Sam, he played before a real audience of punkers who showed their appreciation by spitting at him.

For Harrison’s Flowers, Elie Chouraqui’s tale of genocide in the Balkans, he almost had an eardrum blown out by an explosion. All this was just a warm-up for The Pianist, Roman Polanski’s astounding adaptation of the autobiography of Wladyslaw Szpilman, a Jewish concert pianist who survived the Holocaust in the Warsaw Ghetto. As Szpilman, Brody had two tasks to accomplish before filming began: learn how to play Chopin, and starve himself.

"I lost 30 pounds," he recalls. "I actually had to lose the weight and then gain it back, because of the chronology, shooting the end first. So at rehearsal I was really fit, strong, and I had to lose it all, all the muscle, and then work my way back out of that."

Masochistic though that regimen might seem, Brody felt it was essential.

"I think it’s the only way that I felt would have been appropriate to portray a man in that condition, who is actually a historical figure, and dealing with something as serious as this. And then I felt the responsibility to be as honest as I possibly could with my interpretation. And I felt a responsibility to Roman as well because of his experiences, in Kraków [Polanski was himself a survivor of the Holocaust], and I knew how personal this was for him, so I was incredibly honored to have the role, and it meant a great deal to me."

The weight loss and the Chopin were only the beginning of Brody’s ordeal.

"It took a degree of discipline that I never had to have before. We had six weeks without another actor on the set. He [Polanski] didn’t like using a stand-in, so I had to block every scene, all day, six days a week — long days. I could never let go of this character, for a minute. I’d come home and I’d be exhausted, I couldn’t talk anymore; I was wiped out. I’d spend the day isolating myself. I’d wear earplugs. He [Polanski] would communicate to the crew in Polish, would only talk to me when I needed direction. And I spent the day practicing my keyboard in the trailer, working on the set with the same set of mind, coming home, sleep for a few hours, and come in the next day, do the same."

To imagine the depths of Szpilman’s nightmare, Brody delved into the historical record and into his own personal experience.

"What I had to focus on was a lot of literature that they made available, that I would absorb parts of . . . there was some great documentary footage. But I also had to find a personal connection to that feeling of loss and isolation and deprivation. Not just understanding the time and the specifics of another character, another story. So I isolated myself.

"I’ve experienced loss, I’ve experienced pain, but nothing on that level, and even that wasn’t . . . there’s no comparison, unfortunately. I can’t just conjure up those feelings. But I had to stay immersed in that place. Not just have something to reflect on, and recall, but to experience, to the core. And that’s the only way I felt I could do it justice. And really, it’s insignificant, my hunger and all that. It’s insignificant compared to the hunger that people are really experiencing, because technically, it was optional. If I did become ill, I would have eaten. If something did happen to me, I had an option. It’s not the same feeling as not knowing if there’s another morsel around the corner, and having nothing, and all those things really happening."

Insignificant or not, Brody’s suffering for the role has paid off. He won the 2002Best Actor award from the Boston Society of Film Critics, which also chose Polanski as Best Director and The Pianist as Best Film. The Golden Globes nominated him for Best Actor and the film for Best Picture. Oscars beckon. Meanwhile, he’s taken a role that offers an escape from the brutal realities of The Pianist. He plays a hallucination in Keith Gordon’s adaptation of Dennis Potter’s beloved TV series The Singing Detective.

"Being a hallucination, there is no reality ever," he says. "If you’re just a figure of someone’s imagination and your character doesn’t even know where he is or why he’s there, there are no limits."