Preview: La Finta Giardiniera, Royal Opera House, London

Christopher Maltman walks into the interview room looking as though he's just done a work-out at the gym: I've seldom seen a closer fit for Burt Lancaster in the torso department. But he's been in the rehearsal room, working on his characterisation of the footman Nardo in Mozart's rarely-performed early opera La Finta Giardiniera: Nardo, he says, is a rough diamond, "with more than a touch of the Wayne Rooneys".

With a string of successes behind him, Maltman is now our most accomplished dramatic baritone: when he does a part, you get originality as well as vocal finesse. His recent incarnation of the insinuating Dr Malatesta in Don Pasquale was a case in point: so total was his immersion that his familiar clean-cut persona was simply not recognisable - he'd become someone else. The way he describes the process makes it sound like method acting without the pretension. "I always start with the text, then I try to build up a mental picture of the person - I try on various hats until one of them fits. Nardo is very physical, and I've tried to keep the rough edges on him. When I've got that side sorted, it colours the way I sing. I try to be the way I want to be, and allow the singing to be filtered through that."

He first went into the gym when he had to play Billy Budd. "I just thought, how am I going to do justice to a character who is supposed to be physically beautiful? This was not about anything pompous like sacrificing myself on the altar of my art - it was actually quite selfish, because I ended up feeling a lot better. But it let me off the leash in dramatic terms - the more I could believe in myself, the better I could perform." Since his second child is just eight days old, this discipline is currently standing him in good stead: "When sleep is hard to come by, it helps to be physically fit."

21 September to 7 October (020-7304 4000)