Thandie Newton's discovery of gaiety

Ten years ago, Thandie Newton, then 24, tried to hide from the husband and wife team of Will Smith and Jada Pinkett Smith in a hotel lift. She was in Philadelphia, filming Oprah Winfrey's pet project, the movie adaptation of Toni Morrison's novel Beloved . Newton had just had a massage, and felt she didn't look her best in an oversized hotel dressing gown and slippers. "My face was all shiny from the oil," she recalls, "and in those days I was kind of shy and took myself a lot more seriously than I do now. I was like, 'I'm not worthy', so I'll just disappear, even though there are only three of us in the lift."

Today, Newton is in a ballroom at New York's Waldorf Astoria Hotel to discuss her role opposite Will Smith in The Pursuit of Happyness. She is wearing cartoonishly high Fendi heels and a flirty, navy blue, Marni cocktail dress. Her hair is pulled back and piled high. Looking impossibly glamorous, nothing about the actress says "serious".

Newton was born in 1972 in London to an Englishman and a Zimbabwian mother (a Shona Princess, according to the actress), spending her childhood between her mother's homeland and Penzance, in Cornwall. Since graduating from Downing College, Cambridge, Newton has more often than not undertaken serious acting work: she clearly enjoys opportunities to dig deep in her work.

But, having been accosted by a black American angry at her participation in 2004's vivid ensemble piece about racial tensions in post-9/11 Los Angeles, Crash (for which she won a Bafta), Newton thought long and hard about whether to take on the role of the unsympathetic Linda in The Pursuit of Happyness. Her character, the embittered wife of Smith's failed-salesman-turned-aspiring stockbroker Chris Gardner, performs an act unconscionable for a parent. "You have to think about it as a career move," she admits. "But when I read Linda I did think, 'Oh God, another hateful person.'"

Seeing Newton as she looks in real life - drop-dead gorgeous - points up the quality of her performance. Her plan to be "unrecognisably me" has succeeded, assuredly, with her portrayal of a woman lost in her own torpor. "I wanted to be the first person to feel compassion for Linda. I think there's a terrible habit in our society of trying to erase people who have done bad things. We're all made up of these dark and light shades. I know there are things I regret hugely and they were motivated by unhappiness, fear, insecurity, being young and vulnerable. Now I feel validated, entitled, confident." As well she might. The Pursuit of Happyness is a hit, having opened at number one at the US box office.

Had it not been a formidable season for supporting female performances, Newton could well have emulated Will Smith's Screen Actors' Guild and Golden Globes nominations as Best Actor with a few of her own. But she is thrilled for Smith and hopes to be a fixture on the promotional circuit. "It's going to be so exciting," she enthuses, as if Crash's success has got her in the mood for a little more glitz and recognition.

She is still, after all, letting her hair down, following the movie with two comedies. In Norbit, she is the "other woman" opposite Eddie Murphy, a challenge, given that Murphy also plays her rival for his own heart. And then, "I just didn't want to work after Norbit. I wanted to go home and hang out but Run, Fat Boy, Run was shooting in London, which is very rare, and I love Simon Pegg. David Schwimmer [the director] is a really nice guy, and it wasn't that long a shoot, so I decided to go along with that. I'm so glad because I love that film so much. And Simon Pegg is such a sweet person.I want to be his and his wife Maureen's kid. They haven't had any yet and I'm like, 'Can I be one?'"

Her Bafta award may have something to do with her newly confident, validated, and undeniably playful demeanour And if Newton doesn't feel underrated, then perhaps she should. She has, after all, earned kudos in many films, from Flirting (her 1991 debut), Merchant-Ivory's Jefferson in Paris (opposite Nick Nolte), Gridlock'd, Besieged, and Beloved, to Mission: Impossible II. But she has never been an A-list movie star, though eminently overqualified for the position. Rather, she's happy as a wife and mother, and isn't about to let best time of her career make her lose sight of that.

She is fortunate that her director husband Ol Parker (they married in 1998) is often able to travel to locations with their daughters, Ripley and Nico. This time around, for example, Newton did not require massages to pummel Linda out of her body the way she had the character of Beloved. Children - hers and Will Smith's - took care of that. Newton's refuge from Linda's claustrophobic world were "playdates" with her daughter Ripley, seven-year-old Jaden Smith, who plays Linda and Chris's son, and his sister, Willow.

"I'd take them to the park, or we would go around San Francisco or swimming at the hotel. I got to know Jaden as one of my kids' friends," she says. Newton has no interest in her daughters following her into acting. "No way. No, no, no. Nico doesn't have any concept of what's going on, but Ripley loves coming to my little house on wheels - as we call my trailer. It's always stocked up with stuff for her - Quavers, KitKats, Bedknobs and Broomsticks on DVD - and she loves to hang out there. She feels comfortable. But anything else, no. She's got stuff to do. It's cool for Jaden - he's home-schooled so they can move around. Ripley's not. She loves her school. She's got things to do. And she doesn't want to come with me and sit around for hours on end while they set up the lights."

Not that she says that acting can't be fulfilling. "I worked harder on five or six scenes in The Pursuit of Happyness than I did on the other two films combined. It was fun doing the comedy but it's not as satisfying, partly because, as the girl in the comedy, you're usually the straight woman to give them all time to flutter round. I did get to have some more comedic moments in Run, Fat Boy, Run, but I still felt like I was on hiatus from acting.Simon is the comedian, and he was the one really challenged by the movie. The same with Norbit. I got to support. [But] Eddie's people have been wanting me to make Eddie Murphy films for a long time. He goes through every black actress there is."

She has a point - even Smith, one of the world's most bankable stars, appears mostly opposite black or Latino women. He once confided to me that he'd love to make a romantic comedy with Cameron Diaz but feared that his audience wouldn't accept it. "It's a shame, but it is what it is," laments Newton. "I think if it was done in the right way, where race wouldn't be an issue, it would be great. But you can't bend people's minds too quickly. "

For now, the congested American awards circuit beckons , starting with Monday's Golden Globes. And then? "I'll take that break! I'll see what comes along - but it's nice not to feel pressure. I'm blessed."

The 'Pursuit of Happyness' is on general release; 'Norbit' opens on 9 March