Jude Law's going to surprise a few people with his latest film choice, an ultra-violent action thriller set in the not so distant future.

Jude plays a shaven-haired, pumped-up ex-soldier, who earns his crust slicing people open in order to retrieve artificial body organs they can no longer pay for.

Based on the novel The Repossession Mambo, the film Repo Men depicts a world where humans have extended and improved their lives through the use of sophisticated and expensive artificial organs, known as 'artiforgs'.

But there's a dark side to this medical breakthrough; if you can't pay your bill, an organisation known as The Union will send its highly skilled 'repo men' to take back their property.

It was Jude's agent who recommended he read the script and the Oscar-nominated actor says he was immediately struck by the originality of the concept.

"I liked the dark humour mixed with a love story, a buddy movie and satire, and the challenge that juggling all those tones presented to me as an actor," he says.

In the movie he plays a man called Remy, who Jude describes as "just an upright working bloke doing his job".

"He's been highly trained and encouraged to kill, but then like so many ex-military men, he's been cast off not knowing what to do with his skills at the end of a conflict. Remy finds an outlet through The Union and his bizarre job gives him an epiphany that ultimately sends him on the run."

Despite the blood and gore, Jude says he never felt tentative about the film's violence and if anything it sounds like he embraces its ability to shock.

"I think the graphic nature of the violence is really quite important. I was very impressed that Miguel [Sapochnik, the film's director] saw it through and delivered and that the violence is as shocking as it is," he says.

"These people have this terrible job and they go about it like they're changing tyres on a car you know? They take it for granted and they joke about it and they make bets with one another and yet they're cutting people apart and I think the audience is meant to be shocked and horrified by it because as a society we're getting a little used to watching violence and not really being that moved or upset. You then end up watching the news and not being terribly moved or upset by that either."

For someone whose personal life is often splashed across the front pages of tabloids, and who you'd expect might be quite prickly as a result, Jude is quite the talker. However, there's a sense that his affable nature might become less friendly should questions over his rumoured rekindled romance with former fiancée Sienna Miller arise.

So for now, it's best to keep to safer territory, such as the experience of probing inside prosthetic bodies for artificial organs.

"On various occasions, we had whole bodies that I was allowed to cut into, with working inner organs that I fished around for, wounds that I sealed and weird joints that were able to come out and go back into small knees, hips, hearts, livers, kidneys... all sorts," says Jude with an intense look in his eye and extravagant gestures to demonstrate the "fishing around".

At 37, there may be a hint of a line or two around his green eyes and the hair may be a little receding but the chiselled cheekbones and pretty boy looks that have had fans flocking to cinemas to see him in films such as The Talented Mr Ripley, The Holiday, and Cold Mountain, remain. And today, in dark trousers, a tight white T-shirt and tailored jacket, he looks in good shape, albeit not as defined as was during the filming. But then Jude's the first to admit to the gruelling exercise regime he endured for the role, saying he "can't remember a production more taxing".

To get him in tip-top shape and capable of meeting the demands of the role, Jude moved to Toronto several weeks before shooting began to take part in an intensive training course. It was here the personal trainers behind the super-honed bodies in the film 300 - a film released in 2007, featuring Gerard Butler and many other six-packs - put the actor through a punishing four hours of fight training every day, which was followed by hours of rehearsal with the director.

"I was probably a lot healthier doing this than I've ever been before," he says.

"We had a lot of fight scenes to choreograph but it got us into the right physical and mental state, so that we were fit enough to pull off all the fight scenes and be in that testosterone-driven, macho state of mind," he says sitting on the edge of his chair, puffing out his chest and pretending to flex his biceps.

Alongside Remy, is fellow repo man and his best pal, Jake, played by The Last King of Scotland's, Forest Whitaker.

"Often, you're thrown together and people say, 'That's a good pairing' or 'Those two will look good together', but you never know until you're there whether it's going to work" he says of working with Forest.

"In this case, it worked and on day one it was alchemy. Forest and I recognised the chemistry was good from the get-go, and we immediately knew what we had to do as a pair."

Set about 20 years in the future, the film portrays the world as a particularly dark and cynical place and Jude says he worries "every day" what the future holds for his kids.

He has three children, Rafferty, 13, Iris, 9, and Rudy, 7, with ex-wife Sadie Frost, is step-father to her son Finlay, 19, and in September last year he also became dad to Sophia, who was conceived during a two-week fling with the model Samantha Burke.

"I think one of the issues that concerns me in the film is this sort of laziness, this sort of, 'Aah, if I can do what I want and replace everything then I don't have to look after myself or respect myself,'" he says referencing the option to purchase artificial organs in the film.

"It's almost like, 'I can smoke what I want and I'll change my lungs.' There's a throwaway complacency, and almost a vanity to that," he adds.

"It's like, 'I don't like the colour of my eyes, so I'll change them', rather than learning to live with what we've got and being happy with that."

"I think that theme in the film is on the money."