Liz Robertson is one of our most experienced musical stars, whose West End career began with A Little Night Music, directed by Hal Prince at the Albery. She is current playing Madame Giry in Lord Lloyd Webber's long running hit The Phantom of the Opera, at Her Majesty's. Theatrenow went to meet her.

You've been in an amazing number of shows prior to The Phantom of the Opera. Which role would you say was your favorite? "I suppose Eliza Doolittle in My Fair Lady. It's a wonderful role, though, I think it's often played by people who are a bit too young. When casting it, people seem to think the voice is the only thing that matters and, though it obviously does, you need to be able to act the part convincingly, to bring some experience to it. Another role I really enjoyed was as Maria In The Sound of Music."

Andrew Lloyd Webber apparently wants to stage a production of that in the West End when he can find a theatre. Any chance of you appearing in that? "I'm afraid I'd be a little too old to play Maria now — perhaps the Baroness! I think Maria is a great role, and a better and stronger one than most people give it credit for. It doesn't have to be played in a saccharine way — in fact, I think she's quite a gutsy character, and if you play her like that, you get far more out of it."

You are currently playing a ballet mistress, Madame Giry, in Phantom. Is it just a coincidence that you started your professional career as a dancer? "I think I'm one of only two Madame Girys who have actually been dancers ourselves! I began as a dancer though then concentrated on singing and acting.

"I think it helps in playing this role that I know how the dancers feel, what sheer hard work it is to be a dancer, and how fit they have to be. If you are playing a ballet mistress, then having real experience of dance and a dancer's life is obviously a plus." Given dancers do have to be so fit, why do you think they often (especially the girls) smoke like chimneys? "I really don't know. I'm very involved in raising awareness of the dangers of smoking, and the horrors of lung cancer [her first husband, Alan Jay Lerner, died of lung cancer in 1986], and it distresses me to see these girls smoking. I suppose the main reason is that smoking seems to be an appetite suppressant, so they think it's good for their figures. Also, when you are in your late teens, the idea of dying, say in your late thirties, because of a smoking-related disease, seems so long away as not to matter."

We're talking in the middle of a heat wave. Does this affect your performance onstage, and those of your dancers? It must be hard to dance in those Victorian outfits when the weather's this hot! "We get a fair amount of fresh air onstage, so it's not too bad, but, in fact, for a dancer the worst thing to be is cold. Air conditioning in theatres is great for the audience, and Americans in particular seem to expect it as a matter of course, but for dancers its disastrous.

"However fit you are, your muscles get very tired when you dance, and there's always the risk of injury of pulling or straining them. When it's cold — as it is if you have freezing air-conditioned air blowing across the stage — then you are far more likely to get a strain or other injury — the muscles just seize up.

"When I was in The King and I [playing Anna] with Rudolph Nureyev, in America in the late 1980's, he insisted that none of the theatres we appeared in have their air conditioning turned on. That wasn't very popular with the audiences, but he had enormous respect and concern for the dancers and wasn't prepared to risk their health."

You're currently in one of the best-known musicals in the world. How long are you contracted to appear for? "I have a nine-month contract, which runs from March to November of this year. That suits me very well, not least because my daughter, who is 11, is about to go to boarding school. I chose to have a break from stage work while she was younger, but now she is older and will be away at school. I'm looking forward to more stage work, and I'm delighted to be in Phantom."

A lot of actors seem to be put off by contracts that last more than three months, let alone six or more . "So I gather, but this is a long running show that's clearly going to carry on, so if you have a chance to appear for a good stretch of time, I think you should seize the chance."

How do people keep a long-running show like this fresh? "I think the fact that nine months or so is the longest contract is good, in that you get a regular and reasonably frequent turn-over while still giving people enough time to get into and really enjoy a role. There's also a lot of attention paid to the costumes and the set. I think the costumes in Phantom look fabulous, and the show as whole looks new, not 16 years old! It's this combination of Andrew's music and the production values of the show that keep it so popular. The West End always has a bit of a dip in the summer, but we play to full houses here!"

What's the biggest buzz you get out of being in The Phantom of the Opera? "The applause! We get a standing ovation every night, and that's extraordinary. Being in this show you almost get used to it, but it's not something you can — or should — ever take for granted. But it's wonderful to realize how much people have enjoyed the show, and a great boost to the ego. Obviously people are most appreciative of the Phantom and Christine, but we all share the audience's reaction, which means we go out on a high every night."