Merry lives of Lester

Stephen Sondheim's songs are like speeches set to music - they take you on an emotional journey.

In "Being Alive", for instance, the climactic song from Company, which I performed at the Donmar Warehouse, Bobby starts by saying, "What do you get?" - the words are used to condemn a relationship. Then, halfway through the song, the very same words are used in an opposite way - suddenly, Bobby wants a relationship. The song shakes him into a desire for living.

From what I've heard, doing your average musical can be a bit deadening compared to Sondheim. With most composers, you do not have Sondheim's complexity of emotions. Usually, it's 'I am sad. I am happy. I want love' - very basic - whereas Sondheim is never just dealing with one emotion. With Sondheim, there's a kind of irony tied to each phrase - nothing is ever what it seems. When I was at the National doing Sweeney Todd, for instance, I was playing the young sailor Anthony Hope, who on the surface is a juve lead falling in love. But underneath are many levels - Sondheim dives into them with relish.

I don't know Merrily We Roll Along and won't be able to see it until February, since I'm in Paris playing Hamlet for Peter Brook. But it's great at the Donmar to be able to sing live to an audience without microphones - to really use your voice. I got an Olivier Award for Company, which was really good. It reaffirmed my place in musical theatre because before that I hadn't really been known as a singer. Also, I got to dance in a way I hadn't before, and that has helped a great deal. For me, it was a real coming together in one show of everything I had learned as an actor.