Lucy Punch is making a mark on Hollywood

It's lunchtime at The Beverly Hills Hotel, and Lucy Punch is wading into the shallow end of the pool wearing a white lace Temperley playsuit. As she immerses herself slowly, photogenically, her golden hair fans out across the turquoise water like a Hollywood Ophelia. The jaded Beverly Hills big-shots sitting round the pool barely even notice. Similarly, no one looks up when, during our photo shoot, Daphne Guinness totters down to the pool, wearing sky-high wedges and a cape. It takes a lot to turn heads here, where Elizabeth Taylor and Richard Burton honeymooned in bungalow number five – twice – and Howard Hughes lived for years, imposing his strange requests on the staff (too shy for room service, he used to ask for his beef sandwiches to be left in the crook of a tree in the garden). It was also into this very pool that Katharine Hepburn, hot off the tennis court, dived into the water fully clothed. Lucy Punch emerges, dripping like a post-baptismal starlet.

Later, with towel-dried hair and her long, elegant feet (UK size 9) tucked under her, she talks me through her progress to Hollywood from Putney Common, where she grew up, attending Godolphin & Latymer girls' school in Hammersmith. She is fun, frenetic company. Her voice is as quaintly posh as Joanna Lumley's, but she segues into pitch-perfect impersonations, ventriloquising the frantic tones of a male Italian fashion stylist, the howls of Bagel the beagle, Eric Idle's pet dog, and Freida Pinto's clipped upper-class Mumbai accent. Punch got to know her a little when they were in Toronto promoting the new Woody Allen film, You Will Meet a Tall Dark Stranger. Pinto plays an enigmatic student of the classical guitar; Punch an Essex gold-digger called Charmaine, who preys on Anthony Hopkins. She pulls it off with huge aplomb, creating a riveting, strangely likeable monster, on a par with Alison Steadman's
Beverly in Abigail's Party.

Punch so inhabits Charmaine, all false nails, emotional manipulation and estuary accent, that it is hard to believe the part was first slated for Nicole Kidman, who pulled out due to scheduling conflicts. How does she think Kidman would have played the role? 'Probably better. She's an Oscar-winning actress. What am I saying, probably? Definitely better. I think she'd have made her very Australian.' Punch, on the other hand, used a London dialect, changing Allen's script to anglicise the role. 'He's a New Yorker in his seventies, so he let me change a lot. For example, on paper I was meant to say, "You're in good shape, aren't you?" but I changed it to "You're buff, incha?" ' Punch also suggested music for a scene in her character's favourite nightclub. 'It was a really offensive song called 'Put That Pussy On It' by a band called Spank Rock. When I played it to Anthony Hopkins and Woody Allen their faces went' She mimes frozen horror.

Being cast by Woody Allen has transformed Punch's career: 'A lot of doors opened.' She has just wrapped Bad Teacher, in which she snags Justin Timberlake from Cameron Diaz (Punch says her friends' reaction was: 'That sounds like a very strange film'). She has also been in Dinner For Schmucks, with Steve Carell; made a Nick Cassavetes film called Yellow, and starred as Kate Hudson's best friend in Earthbound. She has become, at 32, hot Hollywood property, because the truism 'talent will out' does, occasionally, come true.

Her first proper part was as Alison Steadman's daughter in the French and Saunders sitcom Let Them Eat Cake. To take the role she dropped her degree course in French and art history at University College London without a second thought. 'They're my complete heroines, great actresses who are clever and don't have any vanity.' It was a pity the 1999 show, set in late-18th-century Versailles, was 'the only thing they've ever done that hasn't been successful,' as she blithely describes it.

Punch has one other BBC stinker on her CV: this year's much-derided cop show Vexed, in which she co-starred with Toby Stephens. She hasn't watched it. 'But my mother told me: "Darling, it's been slammed. Absolutely slammed. Every paper hates it."'

For years Lucy slogged away being very funny in small or supporting roles in cult TV comedies such as the BBC's People Like Us, with Chris Langham, and ITV's Doc Martin, with Martin Clunes. In the theatre she played Jerry Hall's daughter in the stage adaptation of The Graduate in 2000. 'Jerry Hall was just on another level. At the weekend she would go to Marrakech and I'd go to Sainsbury's.' Lucy also did the odd film, including Being Julia, a drama set in the 1930s about actors with Annette Bening and Michael Gambon, and Annie Griffin's 2005 spoof of the Edinburgh fringe, Festival, in which she played Nicky Romanowski, a stand-up comedian so ambitious she becomes Jewish just to get material. She put in a short but hilarious turn as Eve Draper in Edgar Wright's Hot Fuzz. Then she was cast as a lead in The Class, a CBS sitcom about a school reunion by David Crane, one of the creators of Friends, and she packed her bags for Hollywood.

When the show failed to fly, she found herself jobless, in 'the twilight zone' of audition waiting rooms full of 'actresses who look like a vague version of you'. 'I didn't work for a year. It was the longest I'd ever not been in work, and I'd have done anything. Seriously. I'd have done a Doritos commercial, dressed as a cheesy Dorito.'

She recalls her humiliations happily. She once auditioned for a character described as 'really, really sexy', so she turned up in jeans and a low V-neck. The other actresses up for the part had gone more to town. 'One took off her coat and was wearing just a waistcoat. I apologised to the casting director and she said, "Listen, honey, don't worry, you're sexy on the inside."' Just when she thought it couldn't get any worse, the casting director looked her full in the chest and added, 'Don't change a thing, because small is beautiful.'

Lucy never wanted to be Cinderella. 'Never. I always thought that would be so boring. At school I played Miss Havisham. I had an Ugly Sisters-themed birthday party when I was ten. I didn't want to look pretty, I wanted to have a moustache painted on me.' It was a lucrative leaning: she says proudly that she has played an Ugly Sister three times in her career, including in the 2004 film Ella Enchanted, with Anne Hathaway.