There's a moment in the new film adaptation of John Banville's The Sea when suffering, searching hero Ciarán Hinds awakens to find Charlotte Rampling watching, not over him, but across him, with a recondite gaze that simultaneously allows for kindness and cruelty, for ice and fire. Is she here to help or will she eat him for breakfast, we wonder?

“It was a very interesting screenplay, a very poetic piece about memory and recall,” says Rampling. “He wrote beautifully, which is not always the case when novelists adapt their own work.”

The word rampling, one feels, ought to be some kind of lofty verb. How else could one characterise the adventuresome, mercurial oeuvre of Charlotte Rampling?

“I’m attracted to extremes,” she says. “To psychological complexity. Not extremes in sexual or violent behaviour. Those extremes don’t interest me. But bravery matters. I seek out bravery. I need my characters to be brave even when they’re completely flawed and hopeless. Ha.”

The first thing one notes about Charlotte Rampling is how often she laughs. It’s quite disconcerting in someone who is rarely mentioned in a sentence that doesn’t contain the adjective “ice queen”.

“At least they’re noticing me,” she laughs again.

Rampling collaborates with similarly adventuresome directors, appearing in Melancholia for Lars von Trier and Life During Wartime for Todd Solondz. Over the years she propped up at the bar beside Fred Astaire in The Purple Taxi. She was Woody Allen's crazy ex in Stardust Memories. She was slapped in the face by Paul Newman in The Verdict. She romanced a chimpanzee in Nagisa Oshima's playful satire, Max, Mon Amour.

What kind of conversations did they have on that shoot of that last film, I wonder?

“Virtually none! Ha! I had one dinner with Oshima in Paris beforehand. He was a very beautiful, proud man, who spoke very little French or English and he didn’t really like having an interpreter. What he wanted was for us to show him what we could do. He never said what he wanted. And we were only allowed one take, usually. Which is quite often the best.”

At 68, Rampling remains remarkably contemporary. Those unmistakable steely blue eyes and delicate frame – "The Look" as Dirk Bogarde had it – will soon be put to work as the face of Nars, the impossibly hip cosmetics brand. Last year Rampling featured throughout the final season of Dexter as the titular serial killer's neuro-psychiatrist, and performed oral sex in the psychological thriller I, Anna, directed by her son, Barnaby Southcombe.

She’s never balked at sex or nudity. Why not?

“Oh, I don’t know. Ho ho! Story of my life. I’ve always needed to find difficulty, so I could feel that I was evolving. I need a level of challenge. Why do people race cars? Any extreme behaviour is a way of challenging yourself. You need it. You have to put yourself in some danger.”

Rampling has been Rampling for quite some time. Her career began in earnest nearly 50 years ago as a happy adjunct of the Swinging London scene with The Knack . . . and How to Get It and Georgy Girl . In the late 1960s and early 1970s she established herself as the most interesting blot on the Italian cinematic landscape, appearing in Addio Fratello Crudele and Luchino Visconti's The Damned. Was she daunted by the prospect of working with the Italian master?

“No. I was too young and ignorant. I grew up in suburbs and provincial, boring places where you couldn’t see interesting films. I certainly didn’t know about the grand masters of cinema. So the bliss of ignorance allowed me to sail through. I adored him. And he adored me. He lived like a prince and had his court around him. His house and his servants and his cousins and this huge family.”

It sounds like The Leopard.

“Yes, exactly. That’s just how he lived. Except he was in modern costume.”

On The Damned, Rampling met Dirk Bogarde, who talked her into appearing in Liliana Cavani's controversial sadomasochistic drama, The Night Porter, in which a former SS officer hooks up with a concentration camp survivor, 13 years after the war.

“I was aware of the subject matter. But I had Dirk. He selected me. He had read the screenplay four years before. And he called Liliana and said, ‘I’ve found the girl. I want to do your film now.’ So I was very much under his wing. He was extraordinary for me. As a friend, as a mentor. He said, ‘You come with me and we’ll be comrades in arms making this into a love story.’ Liliana wanted to pull it more in an intellectual direction. Trying to make sense of Nazism. It became for me a really powerful lesson in how you can put across an impossible message, really. How you can make a statement through visuals and storyline.”

Rampling was born in Cambridge, the daughter of a painter and an army officer who won gold on the track at the 1936 Berlin Olympics and silver at the 1932 Los Angeles games. Godfrey Rampling died aged 100 in 2009.

“He was a very modest man. We only knew because mum had kept scrapbooks. He was shy. He would never talk about himself. A lot of men didn’t then. Perhaps they still don’t. I don’t know. Like my dad with his running, mum was quiet about her painting. She would never feel pleased with herself about it. My father was a relay runner. I think subconsciously I’ve taken the baton from my parents.”

Army life, says Rampling, would set the tone for her long career. Is that because it instils a sense of temporariness or because it gives one a talent for reinvention?

“Both those things. You’re temporary. And you’re adjusting. You’re never really part of a society. You’re not quite part of the little town or suburb you’re in. You learn to let go at an early age of the sense that you’re going to see these people again. Vague. And you get on with another way of dealing with the world. And film is very close to that in a way. Every time you make a film you adopt a family around you. And you become very close. It’s a temporary family and a temporary society. The stories that you’re telling. But why not? That’s wonderful.”

Army life also goes some way to explaining Rampling’s aptitude for relocation, a gift that has allowed her to become a star of French, Italian and Anglophone cinema.

“I have searched that out too,” she says. “From very early on. I’ve sought out novelty and different languages. I have made that a priority, to penetrate as many cultures and ways of being as possible I can. I’m very much inside my head anyway. I’m very up. I’m very down. I’m very hot. I’m very cold. I’m all that anyway. So then a character joins me. And I’m off the hook for a while. I’m protected. I’m looked after. I have words to speak. And I get to absorb other experiences.”

Following Rampling's Italian period, she relocated to France with her second husband, composer Jean-Michel Jarre, in 1976. They divorced some 20 years later. Since then she has been involved with a Parisian businessman and become a muse for France's younger auteurs, working with Laurent Cantet on Heading South,Dominik Moll on Lemming and François Ozon on Swimming Pool, Sous le Sable, Angel and Young and Pretty.

"When Ozon first phoned me for Swimming Pool we had no money, but I knew that was what I needed to do. It turned out to be a very good move. Of course it could have been a bad move. And that's how I've always done things. The mind chatters endlessly. It can do dastardly things to you. So you need to be guided by instinct.

“Nothing has been a career move. That doesn’t matter to me. That’s not what I’m doing. I’m not doing a career.”

yyy The Sea opens on April 18th