This week the result, The Rise and Fall of Little Voice, transfers to the Aldwych after a sell-out run at the National. It stars Jane Horrocks as a timid Northern girl, shying away from her loud-mouth mother (Alison Steadman), and only coming to life through her ability to take off singers like Bassey, Marilyn Monroe, Edith Piaf and Judy Garland. In a play that celebrates stars and hits, the play's star scores her own. Her strong mix of vulnerability and guts makes Horrocks, at 28, one of the luckiest actresses of her generation. She not only gets plum parts: with both Little Voice and Bad Girl, the BBC play about a single mother whose child is taken into custody, she has got plum parts written expressly for her.
But could Horrocks have mimicked anyone that Cartwright chose for Little Voice? 'It either comes or it doesn't,' she says, when we meet for lunch. 'If you said 'Can you impersonate Alison Steadman?', well, I couldn't. It would have to be a particular voice. A distinctive intonation. I don't analyse it at all. I can either do a person or I can't'
She took to showbiz as a way of impressing her two brothers. 'Particularly my older one. He used to bring his friends home. They were like gods to me. I just wanted them to be attracted to me.' Home is in Rawthenstall, near Burnley: her Dad is a sales rep; her mother is a hospital ward-aid - and a Shirley Bassey fan. They'd watch Bassey on her TV show finish 'If You Go Away', go off and cry, then return to soak up the applause. 'I believed it completely.' After jobs at a bedding factory and as a chamber-maid (they fired her for only working the agreed hours) Horrocks went to drama school. 'It's really ridiculous. You audition for Rada and get in, then you have to audition for Lancashire County Council (for a grant).'
At Rada she played 'endless old women', then left 'and played a lot of 17- year-olds'. In her final year she won the bronze medal (Imogen Stubbs won the silver, Iain Glen the gold). Since then she's worked hard at keeping her face unfamiliar: she had a mop of ginger hair, granny specs and a croaking snarl as the teenage bulimic in Mike Leigh's Life is Sweet; blonde frizz, lots of lipstick and tears rolling down her party-going cheeks in Road; greasy hair swept back and a harried, puckered expression in Bad Girl.
After six feature films the sparky blue eyes, the clear, long jaw line, wide lips and slight bob at the end of her nose, ought to make her stand out. But they don't. 'I get recognised very little,' she says. Across a restaurant table, it's hard to see the characters she's played. Her face is elfin, cheerful, immediate. 'You can paint any picture on it,' she says. 'I hope it's not bland. But no definite features leap out. I haven't got a big nose. Well, slightly big.' She laughs.
What does leap out is her voice. BBC drama producer David Thompson, who hired her for Bad Girl, told me: 'It's not the voice you expect to come out of the face.' She arrives late, wearing a beret squashed low over her eyes, clogs, and black tunic. Here we go, I thought: another ditsy actress. Then out comes this raucous Lancastrian accent, laced with laughter, and these unfettered opinions.
Bad things get dismissed as 'ridiculous', 'horrendous', 'a complete waste of time'. Something really good is 'all right'. When I inform her that David Thompson is thinking of several more projects for her, including a series about a female Walter Mitty, she laughs and says, 'He's all right, is David.'
Shakespeare doesn't fare so well. 'I'm not really interested in classical stuff.' Not Ophelia? 'No.' Why not? 'Not the star of the show, is she?' Horrocks doesn't like doing old plays anyway (though she plays the Joan Plowright role in a BBC production of Wesker's Roots, to be shown in November). 'I don't like the idea of playing a part somebody else has played. I don't want to be compared. I hate to be pigeon-holed. When I started out they said 'Oh, she's like Julie Walters', or 'She's like Gracie Fields'.'
The tag she happily accepts is that of character actress. 'If you wear glasses you keep 'em on, that's what people do. You see people wanting to be glamour girls' - she mimes taking glasses on and off - 'Keep the bloody things on] That's real. Have you ever seen Basic Instinct? The girl - it's ridiculous - on and off, on and off.' (More laughter.) Horrocks has a sex scene in Life is Sweet. She's tied to a bed and her boyfriend is licking chocolate spread off her body. The only thing she has on are her round-rimmed specs.
The star of Little Voice has a small figure and a big voice. And she's all right.
'Little Voice': Cottesloe till Wed (20 restricted-view seats on sale each morning); Aldwych (071-836 6404) from 14 Oct.