Amos is a downtrodden character, quite opposite to Philip Salon in Taboo. Is that why you chose him? "It's always good to play different roles to avoid getting typecast, and I've turned down some other Taboo-style roles. But as much as that is the fact that I've wanted to appear in this show for some time, so when I was offered Amos, I jumped at the chance."

You're a bit younger than the other Amoses. "A Lot! There's nothing definite about his age, though, so you don't have to be 50 to play it. Obviously I'm bringing my own interpretation to the role, and I think he's an interesting character, so I'm looking forward to developing him in the course of the run. Chicago' s fun to work in and has a great cast, with an amazing energy."

You must have needed a lot of energy for your first starring role, as Rusty in Starlight Express? "Well, I had to learn to roller skate and broke my wrist in rehearsals. I really loved playing Rusty — there was lots to do with the role, and I became good friends with Arlene Philips, for whom I auditioned, and who hired me on the spot."

What was it like playing a very different lead role, that of Napoleon? "That was a great challenge, and was in a way every actor's dream — playing the lead in a new West End musical. I did quite a lot of research on the character. I must have read five or six biographies of him, and I went to Paris to look at some of the places he was associated with. He was a fascinating man, of course, and it's always interesting to wonder what made someone like that tick." Napoleon didn't have a very long run... "No, but you can't win them all..."

You won the Olivier for playing Philip Sallon, which must have been a thrill... "It was, and it was also, genuinely, totally unexpected. I hadn't prepared a speech or anything as I assumed it would go to someone from one of the bigger shows, and as well as naturally being pleased for myself that I'd won, I was also pleased for the show, and because it proved that the Oliviers aren't just there to celebrate the large-scale musicals or more 'obvious' plays, but can be won by anyone. They ask you — tell you — not to make a speech thanking friends and family but as mine were in the audience I wanted to. For all the jokes people make about tearful acceptance speeches, it really is a very emotional moment, and my parents have always been there for me and supported me throughout my career, so it seemed natural to thank them."

Did winning it have an immediate effect on your career? "The phone definitely does ring more often after winning an award like that, and it means a few more doors are open, but it's not as though you have to take the phone off the hook or whatever. It's nice to have, though."

You were recently a guest in Anita Louise Coombe's cabaret at Jermyn Street Theatre, where you sang a duet from Sunset Boulevard? "Yes, we're great friends and we wanted to do a duet together — 'Too Much In Love To Care.' During rehearsals we decided to make it a comic version with one or two rewritten lyrics. Actually this dressing room [at the Adelphi] was hers when she was here in Sunset Boulevard."

Do you do much cabaret? "I used to do more when I was in The Lion King and in Starlight Express, but I've got a one-man show that I did recently at the Water Rats Theatre, and I enjoy doing it..."

I saw Ruthie Henshall, who's playing Velma, give a very good master class at the Theatre Royal, Haymarket. Do you teach as well? "Yes, I do about 13 hours a week at Mountview Theatre School. I teach presentation and audition technique: they're very important and not enough attention is usually paid to them. I enjoy working with the students, and it's important that they learn that having talent isn't enough — you have to be able to put it across to the audience."

What do you think is the secret of Chicago's success? It seems to have been putting itself across to audiences very well for six years. "Obviously it's a great show, in terms of the music, the lyrics and the choreography, but the reason this production is still working so well is that it's like a well-oiled machine, and the producers still pay a lot of attention to it. There's a lot of teamwork, and the energy levels are kept very high — the dancers are just fabulous, for example. And although there are frequent cast changes, there's also a sense of continuity — Vanessa Leagh-Hicks has been here since the show opened."

Do you have any plans for after Chicago? "Not at the moment, but we'll see what happens — and in any case I'm concentrating on Amos at the moment. He may be 'Mr. Cellophane,' but he's a very likeable character and audiences have always responded well to whoever's playing him, so he's a good role to get your teeth into!"

Paul Baker can be seen in Chicago at the Adelphi Theatre.