IT'S almost shame to sully Amanda Seyfried by talking about sex.
She sits in an oversized designer chair, feet not touching the floor; shrunk to the size of a child by the furniture. There's something pure about Seyfried, heightened by her waterfall of blonde hair, her doe eyes.
Who'd have thought she'd make such a good porn star?
The reason sex is on the agenda is that for her latest film, Lovelace, Seyfried has transformed into Linda Lovelace, a 1970s sexual icon for her role in the world's most profitable porn film, Deep Throat. Lovelace's turbulent and often unhappy life came to an early close in 2002, when she died in a car crash at the age of 53.
Seyfried, at 27, finally loses some of that grit-your-teeth sweetness audiences saw in musical hits like Mamma Mia and Les Miserables, developing some of Linda's brunette earthiness, fleshing out into porn star curves. Yet what Linda and Amanda really share is the impression of girl-next-door innocence.
In Seyfried's case, she's keen to show that's not reality.
Making a film about Lovelace has been on the Hollywood agenda for nearly 20 years; in 2010, Seyfried's Mean Girls co-star Lindsay Lohan was cast, before later getting dropped from the project. Seyfried said yes to it a year later. She was, she says, well aware of the risk to her career.
"I knew it, and people close to me did not stop reminding me either that it was a risk to take the part. But I wanted a challenge, and it was an unique opportunity."
Not risky in terms of the cast and crew - Peter Sarsgaard gives dimension to Chuck Traynor, Lovelace's abusive ex-husband, and Sharon Stone is unrecognisable as Linda's religious mother Dorothy - but in that Hollywood still doesn't seem to appreciate movies about sex.
After all, Ang Lee missed his Oscar for Brokeback Mountain after sweeping the rest of the awards season. Being naked is apparently the one physical transformation that an actor can make without being in danger of getting an Academy Award for it.
"I would love it if Americans could only appreciate sex in film the way everyone in Europe seems to," Seyfried sighs. "I mean, as far as I'm concerned, it's not that big a deal. I didn't mind the nudity at all in this film, I have no problems taking my clothes off. Not," she adds quickly, "that I'd ever consider doing anything like a porno at all.
"But here in America, there is such a stigma attached to sex. But isn't it better than violence and making movies about people killing each other? Sex is the biggest part of our culture. So why aren't we talking about it in a movie?"
For someone with a reputation for sweetness, backed up by those parts in Les Mis, Mamma Mia and a Nicholas Sparks adaptation, Dear John, this Pennsylvania-born girl really does not have a problem getting naked. She did so two years ago when she played a call girl in erotic thriller Chloe with Julianne Moore.
Perhaps starting off in child modelling at the age of 11 gave her a lack of self-consciousness, but Seyfried claims the opposite is true.
"I actually grew up thinking that sex was absolutely terrifying and that it could kill you. It's taken a while to figure myself out in that way and connect with sex in a healthy way. These roles are a way of challenging myself, of confronting me."
Her frankness is delicious but it must have been excruciating for someone so open about her awkwardness to go through her biggest romantic split in the public eye. Seyfried's most significant relationship to date was with Mamma Mia co-star Dominic Cooper, and confessed she had her heart "well and truly broken" by him.
This year, she has recently hinted that there was someone in her life not from the industry, someone she says she pictures "as the father of her children. But it's a fantasy right now."
Until that happens, she says, it's work and her dog, Finn. Her focus, she says, is to prove herself as something more durable than red-carpet fodder.
"Sometimes I wish I could just go to something like the Oscars in just sweatpants," she jokes, and then sighs again. "But then they'd write bad things and you don't want that. I want to let my work speak for me.
"I now want to take on only roles that challenge me," Seyfried continues, suddenly animated. "Roles that take me to places where I am afraid.
That's the big thing for me. I know there's an image of me as sweet and it would be easy to get stuck into those parts, to be typecast as that female in that kind of film.
"I am privileged that finally there are people out there right now who believe that I can handle the stuff being thrown at me. But I've had to work really hard for that. I really think I'm getting better every year - as an actor that is."
This thirst to prove herself, to keep trying something different, has sometimes led Seyfried badly astray - the schlocky horror Jennifer's Body with Megan Fox, for example, or even Catherine Hardwicke's supposedly erotic twist on a fairy tale with Red Riding Hood in 2011.
However, it also led her to her breakthrough role in 2004 as Karen in Mean Girls. After starting acting when she was 15, taking roles in TV series such as Veronica Mars, Seyfried says she clawed her way into the twisted teen comedy, against the advice of many.
"I really did come into this business from a place of innocence and people did try to exploit me all the time. I had to learn quickly," she says, soberly. "You've got to know your boundaries and insist on making your own choices in life.
"That's why perhaps I related to Linda Lovelace. But she had none of the freedom I enjoy. Her husband wouldn't let her go to the bathroom without permission."
There is little that's erotic about the sex in Lovelace. It's partly just the daily grind of the porn industry, but mainly it's because of the abusive marriage that Linda claims she endured to Chuck Traynor.
Years after Deep Throat was released, Lovelace claimed Traynor had raped her and abused her, forcing her to take part in the film. "Each time you watch Deep Throat," she would say, "you are watching me getting raped."
The absolute truth died with both Lovelace and Traynor more than a decade ago, although both sides of the story are presented by journalists-turned-directors Jeffrey Friedman and Rob Epstein. Seyfried calls the experience of filming, "the most harrowing of my life".
"Not the sex, because actually Peter and I managed to make it really matter of fact. I found filming Chloe far more explicit and graphic. No, it was the violence.
I think we've made it a hard watch, and it only just skims the surface of what she says she went through. It took me to dark places that I found it difficult to let go of. Put it this way," she adds, "I went to the set of Les Mis a few weeks later for the light relief. I only managed to let Linda go there."
Whatever toll it takes, Seyfried says she's "unbelievably proud to have made this film", that whatever glack is thrown at her, she'll stand by this work. "This is a high-profile role for me. I hope this is the game-changer." She looks up and smiles. Sweetly.