And he surely wasn't aware of the hype caused by current Seven Years In Tibet co-star Brad Pitt before filming began. "I didn't know much about him and hadn't read the gossip mags,"says Thewlis, "but I did ask mutual friends if he was a good guy."

Based on the true story of Austrian mountaineers Heinrich Harrer and Peter Aufschnaiter, who set out to climb the Himalayas in 1939 and found spiritual enlightenment, Seven Years was an illuminating experience for Thewlis, too -- of the Hollywood kind. Discovering Pitt to be "a very mellow, easy-going, good-natured, intelligent fellow who is unaffected by all that has happened to him," the actor still wouldn't trade places with the mega-star. "(During filming) in Argentina, I'd go hang out in coffee bars and get to know people. He couldn't. It would cause a public disturbance."

But the lanky Brit, who made an indelible, introductory mark on moviegoers and critics with his desperate, award-winning performance in Mike Leigh's Naked (199?), is embarking on his second, big-budget Hollywood film with Seven Years (his first, The Island Of Dr. Moreau, was "an awful experience, an awful film," he admits). And with it, perhaps, Fame.

Scaling mountaintops in the film, Thewlis shows he'd have the stamina to survive it. "I was sent to the gym for three months, five days a week, to get strong," he says of the regimen that included uphill drills with expert climbers. "It was a greulling, intense period of training which was absolutely essential." While shooting authentic climbing scenes with Pitt, "We had each other's lives in each other's hands more than (producers) will ever know about."

Even more daunting was meeting the real Heinrich, on whose book the film was based, and who was recently revealed to have had a Nazi past. "He is a very verbose man, very egocentric," Thewlis reports, "but also a very charming fellow."

Staying in the spotlight, Thewlis has an upcoming role in a Coen brothers' film, and might do Mike Leigh's next venture, whatever that may be. "He asks me, 'David, do you want to do my next film? I don't know what it's gonna be yet.' " Thewlis mimics, laughing, "which always makes it very hard for him to get the money for it." Not a concern of this thespian, since before his current big-budget lineup, "I was living in a one-room flat, had no money, and was very happy."