Sienna Miller: 'It's good to play a bad girl'

Ever since she was captured frolicking topless with the married actor Balthazar Getty in Italy last year – and again in a bikini top last month – Sienna Miller has been branded as something of a scarlet woman. Therefore, when it was announced that she had lost the coveted role of Maid Marian in Ridley Scott's big-budget Robin Hood, the news was greeted with a certain schadenfreude.

However, meeting with Miller in person in Beverly Hills, to discuss her latest role in the action film G.I. Joe: the Rise of Cobra, it's hard not to empathize with this likeable young woman whose ambitions and dreams are not dissimilar to any other 27 year old. She is both shy and talkative, mischievous and quick-witted, with an engaging demeanour at odds to her tabloid-created alter-ego as temptress and home-wrecker.

Previously twice-engaged (to the actors Jude Law and Rhys Ifans), she looks me in the eye as she says in a barely- audible whisper: "I would like to be married, yes, and I'd love to have a family one day. I haven't always felt that way. I've thought I did in the past, only to realize I wasn't quite ready to settle down and just needed the freedom to be selfish a little while longer."

Press her further and she smiles girlishly, twisting fingers around a stray blonde curl: "I definitely want kids. How many? Ask me in 10 years!"

A veritable chatter-box, who can barely sit still for more than a few seconds, its clear she's more at ease here in Beverly Hills than she has been for many years in the UK, where paparazzi had become a part of her daily life until she decided to take action: "I just couldn't cope with the level of attention. It was relentless. It was just 20 men every day for five years, and whenever I wanted to take my niece out for a walk, it wasn't safe. It just got too much and several things happened. So I sued the paparazzi in Britain for harassment and won, and subsequently have no paparazzi in my life in England. Which is why I feel like a very happy person," she says, whistling softly and making an awkward touch-wood gesture.

"I wouldn't describe it as a restraining order as such, but it was ground-breaking. I was the first person to sue [under new anti-harassment laws] and win, so that now it's illegal for them to be outside my house. And anyone can do it now that I have. I think Lily Allen has just done it too. Basically, they're not allowed to sit outside my house or chase me in cars or take photographs anywhere where I can expect privacy. So unless I'm at an event or at The Ivy, which is not somewhere I'd go, I can't be photographed. And the difference has been like night and day. I absolutely have a life now. I can walk around and take my little niece out to the park, and not have 20 men calling me horrible names in front of her, you know? Don't get me started."

"But England is still definitely my home," insists the New York-born actress, who was a year old when she moved to Britain and grew up in Parsons Green in south-west London. Her parents – she is the daughter of the American banker and art dealer Edward Miller and Josephine, a former model who worked briefly as David Bowie's secretary – divorced when she was a child. And even though the British paps are banished from her life, she admits that she's toying with the idea of moving to Los Angeles: "I still live in London, but I really love it here in Los Angeles. I have a great time when I'm here, but I miss, you know, a good pub when I'm away. I was brought up in Britain and my dog's there, my cottage is there, my garden's there and that always needs pruning. My family are there and its home. I'm definitely an English girl, but at the same time, I really love being able to travel and feel very at home now in LA, because I have close friends here as well as in New York. In all three places where I spend time, I have people that I really look forward to seeing, so I'm pretty comfortable in this little triangle that I'm in.

"Everyone in LA is very positive and upbeat, whereas London can get quite miserable at times. I'd love to move here at some point. I just can't afford to right now. Maybe if I get to do G.I. Joe 3, I'll be able to afford a place, because doing plays on Broadway doesn't really enable house buying," she laughs, referring to her next project, starring as the title character in Patrick Marber's play After Miss Julie.

"It makes me anxious just talking about it. I'm not saying that working on the stage is necessarily any harder – a film can be more grueling – but with a play, you can't drop the ball. You can't go again. And you can't get the giggles on stage, which I've occasionally been known to. It's tough. They're both tough but, you know, the hours are much easier. It's a different style of acting but it's a dream realized to do a play on Broadway," says Miller, who made her London stage debut opposite Helen McCrory and Dominic West in 2005, as Celia in David Lan's production of As You Like It.

"I start rehearsals on 20 August and finish on 20 December. I think the run is 14 weeks. Eight shows a week with Jonny Lee Miller, who is so brilliant. In the meantime, I've got a house in London that I'm trying to sell, and it's obviously a terrible time to try and sell property there. But I'll keep my cottage in the country, which is where I spend most of my time. I'm growing a vegetable patch at the moment, and that's kind of a haven to me. But until I sell my house in London I can't afford anywhere else. It would be useful to have a place in LA because I'm here so much..." she trails off, leaving the question of her uncertain future with Getty dangling mid-air.

Certainly, with Getty by her side, money is a non-issue, given how the Getty name is synonymous with wealth. Miller's beau, who is presently starring in the US TV series Brothers and Sisters, is the son of John Paul Getty III, who was kidnapped in 1973 and had his ear sliced off and mailed to a newspaper in a ransom bid; Balthazar's great-grandfather is the late multi- billionaire Jean Paul Getty, founder of the Getty Oil Company and once one of the richest men in the world. Balthazar Getty, who is 34, has four children with his estranged wife, the fashion designer Rosetta Millington, the youngest of whom was born in October 2007, just 10 months prior to his falling for Miller.

In today's celebrity culture, it's a common misconception that fame equals wealth. Acutely aware that her column inches far outweigh her earning power, Miller nevertheless chooses to work in low-budget independent films – such as Layer Cake, opposite Daniel Craig, and as Andy Warhol's muse Edie Sedgwick in Factory Girl. Leaping at the chance to star opposite Michelle Pfeiffer and Robert De Niro in the fantasy romance Stardust two years ago, her role ultimately took second place to Claire Danes's female lead.

Having first discovered her passion for drama while boarding at the all-girls Heathfield School in Ascot, Berkshire, Miller returned to New York aged 18, to study at the world-renowned Lee Strasberg Theatre and Film Institute, later featuring in several well-received off-Broadway productions.

Prior to launching her film career, she worked as a model for Coca-Cola and Italian Vogue, and posed topless in the 2003 Pirelli calendar. But drama was always in her blood and Miller was almost born in a theatre, her mother having gone into labour while watching the Nutcracker suite in New York in 1981.

If Miller is bitter that her acting talents have thus far been largely overshadowed by her private life – praise for her performance in the 2004 re-make of the 1960s classic, Alfie, for example, was drowned amid the news of her off-screen affair with her co-star Jude Law and his subsequent highly-publicized infidelity with the family nanny – then she tries not to show it. Indeed, she's grown so wary of all the mean things said about her, she even refuses to surf the web. "I never Google myself. Only if I want to feel really terrible about myself would I do that," says Miller, sighing wearily when quizzed about reports of affairs with the actor Josh Hartnett and the British folk-rock singer Marcus Foster.

"What can I say?" she shrugs. She is more open – refreshingly so – talking about herself, her weight and her image. "I'm lucky I have good metabolism and I'm very grateful for that. But it's not toned. At all. And I think I've reached an age where its time for me to start working out a bit. I used to be able to get away with it – I was quite firm and quite tiny, but as I hit 25 things started to change. And now I'm 27, I'm noticing more changes. You know, bare legs at the back is not a pretty sight. I'm lazy and so I wear my clothes so that it's hidden well. But I refuse to worry too much or try to adhere to men's traditional view of sexiness – which isn't so sexy. It shouldn't be so obvious: push-up bras and miniskirts? To me, sexiness is when a woman is comfortable with herself.

"I don't go to a gym. I find that really hard to do. So being forced to get fit for G.I. Joe was fun. I did fight training and boxing and after about a month I had muscles. And it finally gave me the opportunity to play the bad girl – which is how many people perceive me anyway."

As for her private goals? "Keep working. Keep doing this job and, hopefully, be a mum. I think that's enough for now."

'G.I. Joe: the Rise of Cobra' opens on 7 August