Rebel rebel: Why Vincent Cassel is Europe’s most dangerous movie star

You'd think Vincent Cassel must relish trips to London. At least until this year, when he played the lascivious artistic director to Natalie Portman's tormented ballerina in Black Swan, his anonymity was secure on our streets. Yes, he played a limber jewel thief in Ocean's Twelve and a gangster in Eastern Promises. And the eagle-eyed may recall him as the boyfriend of Nicole in a Renault Clio advert. But only those with a taste for provocative French cinema would likely have double-taked had the curly-haired actor walked past them.

Back across the Channel, he's been in the public eye ever since he burst on to screens as a violent skinhead in 1995's La Haine, spearheading a new wave of controversial French films. With a 12-year marriage to Italian actress Monica Bellucci that's kept the gossip rags interested, surely living in Paris can't be easy? He shakes his head. "If you hang out in the wrong place at the wrong moment, and it starts to get a little too excited... it's your fault and you shouldn't be there. But otherwise, I go out by myself at night. It's no problem."

Certainly, it's hard to imagine him a celebrity recluse, locked away in an ivory château. "Vincent Cassel is just the freest of spirits," says Darren Aronofsky, who directed him in Black Swan. "He has a dancer's soul." Even in this Knightsbridge hotel room, dressed in a ragged navy jumper, pinstriped shirt and jeans, he looks fidgety, ready to burst out the window. Those quicksilver blue eyes dart around the room, his words matching them for intensity. He is a bundle of nervous energy, packaged with a devilish smile. "I need to be able to move, travel, jump from one thing to the other," he says. "That's what I like."

The son of the journalist Sabine Litique and the actor Jean-Pierre Cassel, Vincent was a restless and troubled teen. He went to three boarding schools – including a Catholic establishment in which he turned atheist – and ran away from all of them. When his parents split, his mother went to live in New York, allowing Cassel the chance to soak up the city's emerging hip-hop scene (even now, his brother Mathias is part of the rap posse Assassin). If k a four-year spell at a circus school gave him an outlet for his energies, by the time he teamed up with director-friend Mathieu Kassovitz for La Haine, it was given true focus.

While they'd already made 1993's pregnancy tale Métisse together, this was different. The ground-breaking films of their forebears Jean-Luc Godard and François Truffaut – the so-called French New Wave – meant nothing to these street punks. "We were like a bunch of angry kids in a way," recalls Cassel. "Like 'Fuck La Nouvelle Vague, we're going to do something new.' That was the attitude we had." It didn't stop there. From appearances in Jan Kounen's ultra-violent thriller Dobermann to Gaspar Noé's incendiary rape-revenge drama Irréversible – both co-starring Bellucci, whom he'd meet on 1996 thriller L'Appartement – Cassel was like a live hand grenade in their palms.

Now the 44-year-old Cassel is the one pulling the pin. His latest film Our Day Will Come – which he produced, via his company 120 Films – marks the first feature by Romain Gavras, son of the acclaimed Greek-born director Costa-Gavras. Gavras already has a certain notoriety: his epic, nine-minute music video for the hip-hop artist MIA's single "Born Free" – in which a group of redheads are rounded up and made to run across a minefield – was deemed "inappropriate for some users" by YouTube, which insisted they sign in to view it. And no less controversial was his promo for electro-house outfit Justice's "Stress", in which a gang of hooded teens runs riot on the streets of Paris. But, insists Cassel, "They were really beautiful pieces of work – that's why I signed him."

With the title taken from the IRA slogan (which can also be glimpsed on a mural in the "Born Free" video), Our Day Will Come is equally provocative. Like the evil twin to Gavras's MIA promo, it has Cassel playing a psychiatrist named Patrick who takes fellow redhead Rémy (Olivier Barthelemy) under his wing, as they head out on an anarchic road trip across the bleak highways of northern France. "It's about two redheads rebelling against society because they don't want to be bullied any more," says Cassel. "It's a metaphor about minorities, obviously."

Uncompromising and nihilistic, Cassel is at his most subversive and misanthropic here – whether he's making anti-Semitic remarks, masturbating in a communal hot tub or smacking his car into a church wall mid-wedding. Most alarming is his appearance after he shaves his head (recalling La Haine) and eyebrows. "When you do something that drastic, it feels to me like there's nothing to hide behind. What you see is what you get – and you look terrible! But it's good to accept yourself once in a while without anything around. You feel pretty free."

It's his second film with Barthelemy following Sheitan, the 2006 pastoral horror, in which Cassel played (in another hugely unhinged turn) a Satan-worshipping shepherd. The connections don't stop there: Sheitan was directed by Kim Chapiron, a close friend of both Barthelemy and Gavras. As youngsters, together they formed Kourtrajmé, a collective hell-bent on making video shorts by any means possible. "They are of that generation that says, 'I've got a camera and a computer, I don't need any money to do what I want to do,'" says Cassel. "They shoot, edit, shoot, edit. Then they give it away for free."

Cassel's connection with Kourtrajmé stems back to the late 1990s, when he was accosted by Chapiron on the street, asking him to do a fake interview to camera. Later, after making a series of shorts for them, he discovered nobody else in France would take a risk on Chapiron, so produced Sheitan himself. "That's what keeps me alive and excited," he says. Gavras calls him a "godfather" of their collective, an indication of just how Cassel has inspired this next generation of film-makers and actors.

Put him together with Bellucci, and it's a different proposition again. Think Brangelina – but dangerous. When Bellucci was pregnant with her and Cassel's daughter, Deva (now six), she posed naked on the cover of Italian Vanity Fair to protest new Italian laws decreeing that only married couples may use in vitro fertilisation and prohibiting the use of donor sperm. Vatican dignitaries were outraged; the Holy State's newspaper, L'Osservatore Romano, stated: "The child who will be born is no longer a human being to protect in the womb, but becomes the unwitting accomplice of a sad game."

If the couple went through a sticky patch back in 2002, amid rumours that they were living in separate apartments, Bellucci's pregnancy confirmed a union that has held steadfast ever since. And Cassel was fully behind the Vanity Fair cover. "I know that what I see in every religious person is not something I want to teach my kids," he says. He became a father for a second time last May, when Bellucci gave birth to a second daughter, Léonie – and he maintains that this has calmed him. "From my point of view, I'm a totally normal person! Really! I have a family. I have kids. I have a house... I don't have a dog."

Not that fatherhood has stopped his multinational approach to life. He won't move to Hollywood, but with residences in France, Italy and Brazil – he speaks English, French, Italian and Portuguese – Cassel rarely sits still for long. "I don't know if it's more complicated to be moving all the time than stay in one place for a large period of time. It's not like I'm a victim of that life. It's a life I've chosen. So I love it." How do the children take to this peripatetic lifestyle? "My six-year old – she speaks four languages. So it's good for her. It's expensive, but life is short, no?"

He has made nine films with Bellucci now. "And two cartoons and three short movies," he smiles. "We haven't been on stage and we didn't do any documentaries – yet!" Is it simply a way of keeping the family together? "Well, yes, but it's not just for that. When you really like something, you want to share it with people you love – especially if they're talented. We met on set. And then we kept on making movies, so it's really natural for us to work together. There's not another one like her either. So I don't really have a choice, if I want to go in that direction."

With that angular face and wild stare, Cassel may not be a regular sex symbol. But his strength lies in flexibility, in metamorphosis. In 2008, he won a César (the French Oscar) for Best Actor, playing real life gangster Jacques Mesrine in Public Enemy No 1. Gaining 22lb for the role, "I would throw up in the morning, because I was eating too much," he grins. "I had cholesterol for the first time in my life." If La Haine recalled Robert De Niro's breakthrough turn in Mean Streets, this was Cassel's Raging Bull.

His international profile is gaining increasing footing now. Following his shark-like thug in Eastern Promises, Cassel has just completed his second film for David Cronenberg, A Dangerous Method, hotly tipped to premiere at the Venice and Toronto Film Festivals in September. Dealing with the relationship between Sigmund Freud and Carl Jung (played by Viggo Mortensen and Michael Fassbender respectively), there are also two patients thrown into the mix – Keira Knightley and Cassel. "It's actually terrible, because everything I do lately is more or less about the same subject matter," he laughs. "Sex!"

Cassel plays Otto Gross, a gifted analyst according to some, a lunatic to others. "He could have been the successor of Freud," says Cassel. "He was very sharp about his understanding of psychotherapy. But he was on cocaine all the time, opium, and he had babies with everybody. He was really wild." It sounds tailor-made for Cassel. Did he know anything of this world before? "You mean, did I do therapy?" he says, flashing a manic smile. "I did, actually. It was great. I'd do it again!" He bursts into a fit of laughter at this candid revelation – though it's hardly a surprise. Cassel comes on as a man in touch with his inner self.

Reading Jung, the actor was amazed at the connection between the psychiatrist's work and shamanism – which recalls his 2004 film Blueberry, a psychedelic Western that reunited him with Dobermann director Jan Kounen, who became inspired for the film by Cassel's own adventures in the Amazon two years earlier. There, while visiting with the natives, Cassel sampled a potent ayahuasca vine – an experience he describes as "on the edge of being crazy". For him, it was all about tapping into layers beneath the surface. "It's about being free," he says, returning to a theme that defines him.

The actor says that his interest in the subconscious, which began when he was a 17-year-old, reading Carlos Castaneda, is tied in to acting. "I realise the best moment to work is actually when you sleep," he says. Later, he tells me, "I can tell you that I wake up in the middle of the night because I dream about what I do. My unconscious is altered by what I do, so I know it's important for me." It all sounds a long way from the skills of his father – a one-time dancer dubbed "the French Fred Astaire" who was discovered by Gene Kelly and became a screen lover to both Brigitte Bardot and Catherine Deneuve.

Yet Cassel, too, is one of the most physical actors around – just look at his cat-like gymnastics in Ocean's Twelve. "I guess through my father, I had this taste for movement," he concedes. "And maybe on the way I've learnt a bunch of stuff. I like the idea that through what I do, I complete myself as a person. I'm always ready for new experiences. I love when what you do becomes part of your revolution." He pauses, chewing the thought as if it were gum. "I feel very old school and I feel very new school too."

'Our Day Will Come' (18) opens on 29 July and is released on DVD on 22 August on Optimum Home Entertainment. 'A Dangerous Method' will open next year