Interview: Clemence Poésy, French model and actress

• Clemence Posy

Is there a factory hidden somewhere in the Hollywood Hills that manufactures A-list actresses? These women, after all, tend to have a level of polish that seems beyond human, an airbrushed quality that suggests they might evaporate if you reached out to touch them.

Such studied perfection is alien to French actress Clemence Posy, which may be one of the reasons she easily eclipses these living dolls in the style stakes and has quickly become fashion's latest muse.

Today, at home in Paris (she returned only yesterday from the US and is still revelling in "the joy of just seeing people walking in the streets, not driving everywhere") the 27-year-old wears vintage boots, corduroy trousers and what she calls her "grandpa sweater". Her long blonde hair is natural and untamed; simply tucked behind her ears. She often forgoes make-up and rarely wears heels. She is uncommonly pretty, yet she does very little to enhance her features.

Her beauty is strange and magnetic, and indeed she often plays slightly mysterious characters who utterly bewitch the male lead. At first these women appear impossibly angelic, but they soon reveal a darker side. This pattern includes Posy as Chloe, opposite Colin Farrell in 2008's In Bruges, as Emma in 2008's The Third Part of The World and now as Tia, opposite Jim Sturgess in her latest screen outing in Philip Ridley's ultra-dark thriller Heartless.

It seems a little unfair, and indeed a bit vulgar, to dwell on her appearance, yet directors, co-stars, fashion designers and photographers are so taken with it that it cannot be ignored. Martin McDonagh who wrote and directed In Bruges has said of her that "she could access a playfulness, a sweetness that belied her stunning looks," while there is a line in the same film where Farrell's character stares in awe at her face and simply says, "God, you're pretty."

If she's aware of the power of her own looks, she doesn't show it. "I'm always so impressed with these actresses with their perfect make up and hair and sometimes I'm very aware that I'm not like that," she says, a touch self-consciously. "But I don't think I can do things any other way. I would be wearing a disguise if I started to apply that stuff."

What is her relationship with her own appearance? She laughs. She's not sure. "You become aware of it because as an actor it's part of your job in a way," she says in a measured tone. "But I suppose I'm not very concerned with it. It's very weird because in Paris, I can stand in front of an ad with my face on it waiting for the bus and no one recognises me. Because of course none of that is real."

She is being modest, so allow me to fill in the gaps. The ad in question is the perfume campaign for Chlo's signature scent. She was chosen to star in it alongside actress Chlo Sevigny and model Anja Rubik as one of Chlo's three "iconic girls of the moment". Stylists and photographers adore her thanks to her French insouciance and quirky sense of style: she regularly features in fashion magazines including Vogue and Harpers Bazaar, and has graced the covers of style bibles from ID to Nylon and Tatler.

She is something of a muse to Balenciaga's Nicolas Ghesquire and to Karl Lagerfeld of Chanel, where she regularly sits in the front row.

Indeed, so in demand is she for fashion shoots that she recently made the decision to stop doing them altogether unless she was publicising a film: "When it comes to photoshoots, there was a clear moment for me when I thought 'I'm going to have to enjoy this because it's going to be a part of what I do.' The minute you start to enjoy it and to keep that playfulness, it does become fun, but I reached a point when I stopped doing photoshoots that weren't a part of my job because it didn't feel quite right."

How does she feel about being considered a style icon? "It feels strange. It feels random. I love fashion, and I've always wanted to do costume design, but I'm in jeans and T-shirts most of the time. I don't know what happens to make people put you in that little box, but I certainly don't mind it."

She is a woman who women want to be friends with. She lives alone in Paris, where she's something of an "it" girl. She has been described as both a "future icon of French cinema" and "a young Jane Birkin". She wasn't popular at school, and firmly believes that that contributed to her artistic success today. She is imperfect; her teeth are quirky, and she has described herself as having a "bizarre face that's a bit out of proportion". She says her greatest strength is having "a good ability to enjoy life" but says she has too many weaknesses to list.

Born and brought up in Paris, Posy is the daughter of a French teacher and a theatre director, and was immersed in the arts from an early age. Her parents fed her the lie that their television was permanently broken, so she never watched it. Instead, they passed on their enthusiasm for film, theatre and literature. Her upbringing was, she says, "very peaceful, loving, caring, and I have a beautiful relationship with my family. I am thankful every day for my happy childhood."

She attended an alternative school in Meudon, before spending her final year at the cole Alsacienne – the most elite school in Paris – thanks to a scholarship offered to teachers' children. She was considered a bit odd at school, and rebelled a little against her alternative family, spending a year in her teens plastering herself in make-up (it was actively discouraged by her parents) and watching lots of television. Time spent at a school in Canada taught her that popularity is a hollow concept when she suddenly experienced it for no particular reason upon arrival in this new environment, finding it more than a little discomforting.

By the time she began studying drama in Paris she already had an agent (although she "sort of never wanted to be an actress. I found it a bit embarrassing because that's what all the little girls said they wanted to be when they grew up") and went on to gain roles in a number of French film, television and stage productions.

"Someone once asked me why I'm doing this and I didn't have an answer," she says with a laugh. "My sister (the actress Malle Posy-Guichard] and I played a lot. We invented a lot of stories and I suppose that acting is a bit of an extension of that. But for me I never had that thing where I would feel ridiculous. You find yourself in situations where you think 'oh my god, what am I doing, what am I saying?' And I suppose if I didn't have that joy as a child, that ability to not care, to not be self conscious and to tell stories, well I suppose it would be unbearable! It's the easiest thing to do if you have that unselfconsciousness. It's that element of being a kid and playing at being a cowboy, and believing it entirely until your mother calls you in for dinner. It's a beautiful job."

Her first English-speaking role came when she played Mary, Queen of Scots in the 2004 BBC mini-series Gunpowder, Treason & Plot (she has "a very special tenderness" for the Scots and is desperate to visit Edinburgh during the festival). In 2005 she played the ethereal Fleur Delacour in Harry Potter and the Goblet of Fire, and starred in a number of film and television productions, including the 2007 mini-series War and Peace.

In Bruges helped to put her on the map, and this year she will star opposite Rupert Friend and Forrest Whittaker in Benot Philippon's Lullaby for Pi, in addition to her role in Heartless. As with In Bruges, she selected the role, not so much because of her attraction to the character, but to the story itself.

"I remember feeling how dark and scary it was just reading the words in the script," she says. "It was so different to anything I had ever done and I was curious. I wanted to be a part of this film. There are no rules as to what motivates me when it comes to choosing a role – it's often about working with a particular director or opposite another actor. Or it can be about finding a balance between dark and light, between heavy, serious roles and more fun ones. With Heartless, I liked that my character is so pure in such a dark world, even if she is not as white and transparent as she seems at first. There's a real sense of innocence there."

Posy has arrived at an interesting point in her career and in her life. She may not be recognised by her fellow Parisians (whom she says are too cool to admit to recognising anyone anyway) but her star is on the up, and as she takes on more mainstream roles, coupled with the fashion world's obsession with her, she may no longer be able to catch the bus without being spotted.

She refuses to be drawn on her private life, but reports suggest that she is in a long-term relationship. For now, her partner's identity remains unknown, but she fears a level of fame where things might change.

"When it comes to fame I am in a very convenient position," she says apprehensively. "I live a very normal life. I have met people who have a level of fame that completely changed their lives, but where I'm at, it's really nice. Sometimes people come up to you to say that they enjoyed a film you were in, which is very nice, but that's about it. I would like everything to stop where it is right now. As for the rest, I'm very happy, very content. And if I lose that fun element, that joy, well then maybe I'll try something else. I don't like to make plans."

Clemence Posy may not have plans for her career, but her career certainly has plans for her. Like all the leading male characters she plays opposite, both Hollywood and the fashion world have fallen head over heels in love with her beguiling beauty, Gallic charm and that je ne sais quoi that doesn't allow you to take your eyes off her. Far from being forged in some factory churning out identikit actresses, she breaks the mould in the best possible way.

Heartless is released on 21 May in cinemas and 24 May on DVD and Blu-ray.

This article was first published in The Scotsman on 15 May.