Sienna Miller's latest silver screen project sees her playing a sex kitten starlet opposite Steve Buscemi's veteran war correspondent. Interview opens in cinemas across the UK today, and Miller chats about her current film role.

Were you at all intimidated by playing this character, with people perhaps seeing Katya as an extension of yourself, with all the surface similarities?

"If the character convinces them, then I’ve done my job, but frankly, like you say, she’s a very different personality. Obviously, the circumstances are similar. She’s an actress. I’m an actress. She’s known more by reputation than for her films and I think that’s something I can definitely relate to, but she’s actually complex, layered, and manipulative, and fascinating. As an actress, it’s just a perfect role to play, just such an ideal film. And also to have Steve Buscemi in the same room acting opposite you is just a dream come true."

You spent a lot of time together. I hope you liked him!

"I loved him. You can tell we got on when you see the film. You can tell there’s good energy, chemistry and all of those things, but it is hard not to get on with him; he is such a wonderful man. He had a lot of work on his hands but we had this great intensity in a two-week rehearsal, where he did a lot of directing, and so once we got to shooting we were at a place where we were very comfortable with the script, comfortable with what was going on, and therefore we had room to improvise and move around."

I was going to ask you if you could improvise with something like that? It was so open and with only two people to direct…

"Yes, we did. You add something, you play around, because it was two of us, and because we were not creatively restricted. It was three hand-held cameras, and there were no marks to hit, and there was no continuity, because they were constantly capturing every angle of one scene. So, when, for example, I ran and dive onto the sofa I just decided to do that in the moment and they caught it."

It was a fine dive; did you dive at school!?

"No, but I dive at home often. It was just really creatively liberating as a piece."

Is Katya troubled or just a young girl having fun?

"I actually don’t think that she is troubled. I think she knows who she is, she understands where she’s at and she knows what she likes. She’s very strong, conniving, and manipulative but only in retaliation to his sort of manipulation. But I don’t think she’s troubled. I think that she is absolutely existentially content with who she is, and why she is."

That is an impressive word!

"It just means that you are responsible for what you do and for why you do it, but it is not definitely preordained. You choose your actions and take responsibility for the consequences."

And that is what you like about her?

"Well, I just think that’s one of the things she is and I respect that quality. It’s not like me. She’s complex, so layered, and it sort of happens instinctually, and a lot of it happens there in the script. We were doing eight-minute takes and you forget there are cameramen there, and then there was thirty page of dialogue a night. It was a nine-night shoot, the entire film, so really, it felt like doing a play."

Are journalists sometimes badly prepared, like Pierre in the film?

"No. I have had some who are absolutely completely disinterested in any opinion that I may have, but are unashamedly content to ask things that I would find embarrassing to ask someone I didn’t know. That’s just a lack of respect. I have been in those situations, but now I don’t have any time for it. Before, I was so eager to please, but now you know who is interviewing you, and I can control which publications I can speak to."

Did the subject matter of the film create any understanding, appreciation or sympathy for journalists?

"I think that journalism is a really important medium, and that it gets abused and therefore has a bad reputation, but journalists have a massive, important, and powerful responsibility. Certain journalists abuse that power. I think it is an obviously incredibly important medium."

Even for the toy departments of journalism, like sport and film?

"Yes."

Good. Thanks! From what I have read you are quite a good interviewee…

"Am I? Do you think? I guess that I am open. I wish I were less open because it tends to get me into trouble a bit! I find, essentially, what you are doing is putting yourself up for judgement so it’s quite a weird dynamic. I’d rather be myself though. I’ve heard people say ‘Just play a role, just talk about the film, just be composed, and don’t give them anything’. Frankly, I’d just rather have a good chat, personally, for my own sanity as much as yours, and you know at the end of the day, if someone wants to abuse that openness that’s their decision. I’d rather be myself and I think I’d be unhappy trying to be someone else."

By that rationale, can you enjoy it?

"I have done interviews that I really enjoyed."

Even at junkets?

"On junket days it’s really hard but this interview we’re having is like a chat, you know what I mean? It doesn’t feel like it’s an interview. But when you are doing films, a junket does get quite exhausting after a while because you repeat yourself."

All these quotes you’ve given me, you’ve given everyone else then!

"No, no. I haven’t (laughs)! But it is tiring trying to think of new ways of saying things, and inevitably you do end up repeating yourself, because you get asked similar questions."

Do you ever decide beforehand what are the things you’d like to talk about?

"I think I like it when people want to talk about things other than the personal. That’s always appreciated. If people are interested in views on work and all of that and I like playing games, the Stones vs The Beatles; Star Trek or Star Wars. I love all of those. But, you know, at the end of the day if it’s a good journalist, then it is a good conversation. It can be quite thought provoking, and interesting but I am not mad about talking about myself. I always try to turn it round on someone else. It’s interesting, but you are being analysed to a certain degree, and some people obviously feel understandably threatened by that. It is something I haven’t analysed, but I have met journalists and have had really good conversations. I’ve also done interviews where I have felt totally taken advantage of and felt really unhappy about the outcome."

Recently or in the past?

"When I was younger it happened more. I think now I am sort of more aware if someone is trying to do it. Some are out to get you, and there’s a lack of respect and I sense it. I always know when it’s going to come out wrong. I do have a big gob. Sorry! That’s my publicist over there smiling!"

So who’s stitched you up recently?

"It usually happened before I had a publicist. Just certain journalists, you just know what they are after. Steve and I did a whole interview session in Sundance for this film, and a journalist interviewed me. It was all about swag, the gifting that goes on at the festival. I didn’t do any of that, but the article was all about what I’d be given. It was nothing about the film, and it’s disappointing."

So is it easy for you to separate journalistic types?

"I think you know when someone’s judgemental, and you sense when people are out to get a certain thing. I’m more astute now than I was, and am better at deflecting things, and I’m much better now at saying ‘Actually, that’s none of your business!’ Whereas before I didn’t want to offend people, and it’d be at the expense of my personal wellbeing that I’d try and make them feel comfortable by answering a question that I didn’t necessarily want to answer.

Do most people usually back off now?

"Some are quite persistent, and then it gets argumentative and I get defensive, which is awkward and tense. People say things like, ‘You cannot deny that you’re a public person, so why don’t you want to talk about it?’ Well, simply because I don’t want to, so they should bugger off!"

Being a popular subject for the tabloids, is that a help or a hindrance?

"A hindrance. Definitely. I think as an actor, if you can retain a level of anonymity, then people are more likely to believe the characters you’re playing. The more people think they know about your private life, the harder it is for them to see you as anything but you, when they go and see a film. So that kind of attention isn’t great. An interview in The Times or The Guardian,or any more intellectual newspaper that you want to name, is useful, but someone getting a photo of you blinking and then saying that you’re drunk, well that’s not at all helpful to your career. And they do big smear campaigns, building you up and knocking you down. But really, in the bigger picture, people are starving, and there’s a war on. We live in a small island and while these things seem monumental at the time, and are big in the small world that you live in, in the grand scheme of things it’s not important to me. I’d take the media on if I see a window, but I’m not going to lose sleep over something I can’t control. There’s no point; essentially I’m a happy person, and that’s what’s important."

Surely even journalists from the broadsheets still ask about your private life…

"They do, but in a more interesting way. They’re seemingly more interested in what the effect is on me, rather than who I’m dating. It’s a more analytical approach, rather than just ‘Dish the dirt!’"

Have many people today asked you whom you’re dating?

"They’ve tried! But they’ve been deflected. People try and be all chummy about it, and think that you won’t see what they’re really doing!"

With Alfie and Layer Cake…

"They were my first two films…"

But they do trade on your sexiness?

"Well for Layer Cake I think we could call it gratuitous! But that was my first film, and it was a great film with great actors. She’s a gangster’s moll, and it was a gratuitous role — there wasn’t that much acting involved — but I was 19 and I got offered a film. I didn’t get my knockers out; I was just in my bra and knickers, but she was still a character, I thought! Because of what had happened in my private life, a huge amount of focus was on that film — but I don’t regret it. It was a great movie. There was such a focus on me, and who I really was, at the time, that I think it got more attention than if someone else was just starting out."

Why has it escalated so much for you?

"Because I was famous before I had a film come out, so I was tabloid fodder and someone’s girlfriend, before I was an actress, so it’s a slow process trying to break down those preconceptions and be taken seriously as an actor. Hopefully, I’ll get there! It might just take a bit longer for me."

Don’t you feel as though things are changing for you now?

"I do, I sense that. Just Steve Buscemi phoning me up and asking me to be in his movie, that was amazing. Whenever I do feel down, I just think of that. He was one of my heroes, and if I’m good enough to be in his film, then that makes me feel like a proper actor."

So what did Steve Buscemi say when he called?

"He called — which was amazing in itself — and he said that he was directing a movie, it was a two-hander, and would I be interested in reading it. I just said that I’d do it, there and then. He asked whether I should at least read it first and I said, ‘No, I’d come and make the tea on your film set, mate!’ And it turned out to be a fascinating piece, and while I was very uncool and very available, but if he called, you just say yes. He is so intelligent, and has huge integrity, as a man and as a filmmaker. He’s an all round great person."

So how long was the entire process?

"It was just nine days of shooting and then two weeks of rehearsal before that. It was very small, a little window. But it’s a great film and it’s the first time I’ve done something where I can appreciate it as a piece of art, and as his vision. It’s an interesting film for me, although I still don’t like watching myself."

Is it always like that for you?

"Yes, it’s like when you hear your own voice, although about 20 times worse! It’s awkward, although then you do learn not to be narcissistic about it, and learn to watch it as the director’s vision. It’s their film; you can disassociate yourself, and certainly I don’t sit at home watching all my films. I’ve seen each one a couple of times, but that’s it."

I should imagine this film was very intense to shoot…

"It was; 30 pages of dialogue a night, eight-minute takes, it was intense. But it was thrilling as an actor to really act, and throw yourself into something like that. It was a dream job."

What films of Steve’s did you most admire?

"I loved Fargo; he was brilliant in that. But everything. I loved Trees Lounge, which he also directed, and Reservoir Dogs, and even in Con-Air and Armageddon, these big commercial films, he’s always brilliant. He raises the bar in all those films. But I do love Fargo."

Katya says that there’s always a winner and a loser in a relationship. Do you feel there’s some truth in that?

"I don’t look at life like that; that’s too black and white. I feel like relationships are all about colours and grey areas. I guess when you split up there might be a winner and a loser. I try not to see life in that way. I never really understood that line, when I think of it. I guess it depends whether there’s game playing involved in the relationship, and with those two characters, I guess there would be. But people who aren’t manipulative wouldn’t be in a game-playing relationship. For the characters it’s a power struggle; it’s like playing with your food before you eat it. That’s how they are with each other, but I’m not that kind of person."

Is there an answer to Pierre’s question ‘What makes a man attractive?’

"For me, it’s a sense of humour. If someone makes me laugh, then I find them instantly attractive, because I want to be around them. That’s the most important thing to me, not scars, not even psychological scars, because everybody’s got them. I know it’s a boring answer, but if people make me laugh, then that’s a big bonus."

This is a big year for you, with the films you’re working on. Does it feel that way?

"No, I’m a day by day person. I try and live spontaneously. I’m exited that I’ve had the chance to work with John Maybury, and with Steve, people I really respect as artists. And Kiera Knightley. I feel happy and lucky and things are going well but I try not to analyse them too much."

Have you become friends with Keira?

"Yes, we’re going to have a drink later. I loved working with her, and having a partner in crime, someone who understands the harder aspect of what we do. I don’t want to sound like a whiner, but it was nice to have someone who understood those things. I love her and think she’s very talented."

Interview is released in the UK on Friday 2nd November, 2007