At the top of an actor's CV, alongside height, eye colour and the like, comes the phrase 'Playing Age'. This rather elastic term translates as: whatever you think you can get away with. Hoardes of naive drama school graduates make unconvincing claims of being able to play 30-year-olds. Most casting directors would smirk at the prospect of a 23-year-old being able to pass for 12 but Tamblyn Lord has been doing it very successfully for the past two years.

'It was such a good role I'd have been mad to turn it down. I'd be lying if I said I didn't worry about constantly playing a twelve-year-old, but this was only supposed to be a four-week job.' The job in question is the lead role in the hit play Two Weeks with the Queen which opens tonight at the National Theatre in a new production directed by Alan Ayckbourn.

Twelve-year-old Colin is sent from Australia to England because his parents want to shield him from his brother's imminent death. To the horror of his suburban British relatives, Colin plots to meet the Queen to pick her brains about curing the cancer. Unsurprisingly, his breathless enthusiasm doesn't yield the expected results. For a play so concerned with death, it is extraordinarily funny and energetic. And it's very moving. If cancer-drama conjures up Bette Davis being tight-lipped in Dark Victory, think again.

'It isn't 'a comedy' or 'a drama', it's both,' says Lord. 'Audiences laugh and cry. It doesn't matter how old you are, it touches base with all ages.' For once, this sweeping statement is true. Australian audiences were split between children and adults and the play is an adaptation of a children's book. . . one which covers cancer, Aids, a gay relationship and the Amazon Jungle.

'Every time someone asks me, I think the play is about something else. At the moment, it's about growing up and losing naivety. It's hugely important as a piece for young people, and not just because it is so matter-of-fact about Aids. Children are so often denied their feelings about grief. This speaks to them rather than at them.'

How does the production compare with the original? 'It's less cartoonish. The characters are more earthed. He (Ayckbourn) has found lots of English humour in it. I was afraid he might show Australians as a bunch of guys in flip-flops and shorts with stubbies. There's more to us than you see on Australian soaps.'

'Two Weeks with the Queen' opens tonight at the National Theatre: box office 071-928 2252

(Photograph omitted)