Many have remarked that the most memorable performance in the "Lord of the Rings" films is given by a computer-generated character, Gollum. But let's not forget the man behind the critter, British screen and stage actor Andy Serkis, seen in films like Mike Leigh's "Topsy Turvy" and Michael Winterbottom's "24 Hour Party People."

In an approach that was nothing short of groundbreaking, director Peter Jackson had Serkis perform his scenes on set in a specially wired motion-capture suit, and his movements and facial expressions became the basis for the animated Gollum. Serkis spoke with me about his four-year experience of working on the trilogy, and the irony of being one of its best-known but least-recognizable stars. And I made sure not to wear any rings to the interview -- Serkis has a habit of slipping all-too-convincingly into character at any moment.

No matter how good the animation for Gollum is, it's the voice that really sells it, and you got it just right. How did you go about developing the voice?