Diane Kruger: The unknown side of the star who launched a thousand ships

The star didn't get into modelling and movies for the glamour. James Mottram meets an actress determined to engage with the real world

It all feels very full circle. A year ago, Diane Kruger was in Berlin shooting Unknown, the new conspiracy thriller starring Liam Neeson that has just bowed at Number 1 in the US. Now, she's back in the city promoting the film while staying in the Adlon Hotel – the one that Michael Jackson dangled his child out of, which features heavily in the movie. "I feel like they gave me the Eisenhower suite," she laughs, referring to the fictitious room that Neeson's biotech scientist checks into before a car accident sets a head-spinning series of events in motion.

In truth, Kruger is not one for fancy hotels. Never mind the fact that she's a former model who got her Hollywood break as the beautiful Helen in Troy and cemented her status as a spy in Quentin Tarantino's Inglourious Basterds; the German-born blonde prefers simpler comforts. When she was living in Berlin for Unknown, unlike other cast members who stayed at the Adlon, she had her own apartment. "I don't want to live my life in a five-star hotel," she shrugs. "That's not real life to me. You can't appreciate it. It's lovely to stay in a beautiful suite but that's not real life."

In the past couple of years, Kruger has backpacked through China and Australia with her boyfriend, the actor Joshua Jackson. She's just returned from Tjakistan, too, where she endured a hellish-sounding shoot for the Taliban-kidnap drama Special Forces. "I've never felt such cold," she says. "Seriously, just to give you an idea, they built an igloo to keep us warm. When they said, 'Do you want to go step inside the igloo?', I was like, 'You're fucking kidding, right?' I never thought I'd hear that!"

Admittedly, it's hard to imagine the perfectly sculpted Kruger, with her flawless cheekbones and expertly manicured nails, roughing it like this. "I know a lot of people think, 'She's so glamorous.' But that's really not me at all," she argues. "I'm not from that background. I'm not that person." There's an earthiness about Kruger. Looking out at the traffic flowing past Berlin's Brandenburg Gate, she tells me she learnt to drive on the streets of Paris. "I can handle myself – I'm a big curser!" she chuckles.

Born in the tiny hamlet of Algermissen, some 20 kilometres south-east of Hanover, she "grew up humbly", she says – "not poor but lower-middle class". Her father, Hans, a former cinema projectionist, also battled with alcoholism. "I don't want to sound like a sob story," she says. "Everyone has issues. But because of my Dad's illness, my Mum had to go through a lot. She was the one that had to go to work and raise us kids alone. She was strong – but because I was the eldest, I definitely saw her doubts and fears and her struggles as a woman."

While Kruger's parents went through an ugly divorce when she was 13, she was left to look after her younger brother Stefan while her mother Maria-Theresa worked in a bank to support them. Although Kruger's mother made sure her daughter "touched on every aspect of life" – from learning the clarinet to training to be a ballet dancer – her father's addictions also left a mark. "Because of my Dad, I was never tempted by drugs or alcohol [when I was young]," she says. Instead, she ploughed her energies into ballet, even studying at the Royal Academy in Hanover, until a knee injury sidelined her and forced a rethink.

By the time she was 15, she had started on a second career, having won a modelling competition. It wasn't the promise of glamour that tempted her: "It allowed me to travel all over the world," she reasons.

After moving to Paris – which she thinks of as home – she landed on the cover of French Elle and later became the face of the Armani scent Acqua di Giò. But, by the age of 22, she'd had enough: "Modelling is so... not superficial. Well, I guess it is. But it's boring." Acting was the obvious next step, as a way to keep travelling while creating something more substantial.

Using the money she'd saved from working, she quit modelling and enrolled in the Cours Florent drama school in Paris. Not long afterwards, she met Guillaume Canet, the French actor-director best known to international audiences for his part as a backpacker in The Beach. They married in 2001, and a year later Kruger appeared opposite Canet in his directorial debut, Mon Idole, which won her a Best Actress César nomination in France. They reunited in 2005 to star in the First World War trenches tale Joyeux Noël – in which Kruger played a Danish opera singer – but, 12 months later, the year she turned 30, they divorced.

By this point, Kruger was a star-in-waiting, thanks to roles in Troy and the Nicolas Cage-starring action-adventure National Treasure. But to her, becoming a citizen of the world was more important. "Getting older, I realised I didn't know anything," she says. "I felt incredibly stupid. I've always been very self-righteous. I've always been like, 'I speak three different languages, I'm so accomplished.' And everyone tells me, 'You're so pretty', and then it was a big realisation that I don't understand anything, that I feel like I'm not cultured enough, that I'm stupid sometimes."

Now 34, Kruger has reached a new level of self-exploration. "That's my thing in my thirties," she says. "I want to work on 'me' much more." This is partly due to meeting Joshua Jackson, the Vancouver-born star of Dawson's Creek, in 2006. Jackson not only instilled a love of ice hockey in Kruger. "Josh is someone who is very grounded," she says. "It's pure, there's no bullshit. He is very curious and is someone who always reads and is very politically engaged. He awakened the urge to ask more questions. You can take so many things for granted, because you read them and think it must be true, and he's not like that."

For Special Forces, she spent four months interviewing female kidnap victims in Gaza and Afghanistan as part of her research to play a French journalist who is taken by the Taliban. Then came weeks of shooting in Africa and the Himalayas, with no access to the phone or the internet. Kruger admits she was "horrible to everybody" without her home comforts, but claims the experience "really changed" her. "I just thought it was fascinating on a personal level. How many times have I been at home, cooking dinner and the TV news is on, and you're like, 'Ugh! Turn this off!' You take for granted that you have access to information."

Even her role in Unknown has a political edge. She plays Gina, a Bosnian illegal immigrant cab driver who helps Neeson's character after he wakes up from his accident to discover that nobody recognises him and his identity has been stolen. It's not the first time she's mastered the accent, having briefly played a girl from the country in the Bosnian war drama The Hunting Party, but Unknown is different. "Obviously, this is not the kind of movie that is going to go into any deep detail. But we learn that she's watched her entire family be assassinated. And I just thought it was interesting in a movie like this – a genre film – to have a little bit of a social background."

With Gina looking anything but glam in her jeans and Dr Martens boots, Unknown is also a marker of how far Kruger has come since working with Tarantino. No longer is she saddled with arm-candy roles. "I feel like before Inglourious Basterds, in America, they would've probably offered me the part played by January Jones [the Mad Men star plays Neeson's trophy wife], because that's a more obvious part for me to play. So I loved it that they offered me this. It's cool to think they said, 'Illegal Bosnian immigrant taxi driver – let's get Diane Kruger!' I'm not sure that would've been the obvious thing before."

With no desire to move permanently to the US ("I love America, but I don't see myself growing old there," she says), Kruger is determined to pursue an international career. Having acted in French before (most successfully as an imprisoned spouse in Anything for Her), she's preparing to play Marie Antoinette for the French director Benoît Jacquot in Farewell, My Queen, with the story set to concentrate on the monarch's final days in Versailles. "I'm a little sweaty about it," she says. "I am. I'm a little nervous about it. She's a big historic figure, so big shoes to fill."

Of course, she's been there before as Helen of Troy, a role which could've ended her career before it even began. "That was the last time I read reviews!" she says. "According to the critics, my career was almost done. Where was I going to go from there?" Indeed, it would seem almost impossible to follow playing the most beautiful woman in the world. "I think I was perceived as such a European, dainty, pretty actress," she laughs. Not any more: from cab driving in Berlin to the Himalayas, Kruger has learnt that A-list luxury does not always keep your career alive.

'Unknown' opens on 4 March