If his tabloid profile is to be believed, Jim Threapleton cuts a forlorn figure these days. After all, this is a struggling film-maker who had the temerity to marry a British national treasure before she left him behind. Threapleton is the former husband of Kate Winslet and the father of her seven-year-old daughter Mia. Married in 1998, they divorced three years later. She went off to enjoy a fairytale romance with the Oscar-winning director Sam Mendes and he sank back into obscurity.

But when we meet, Threapleton looks far from being a broken man, reduced to spending his days in his local pub. It was for painting just such a portrait that he took action against The Daily Mail after the paper suggested that “I was doing nothing and I had nothing going on”. It was a false image he had lived with ever since he met Winslet on the set of Hideous Kinky (1997).

It was never his intention to use Winslet as his way into the film industry. “I think sometimes people expected that I could just instantly say: ‘Hey, guess who I’m married to! Give me £3 million,’ ” he says. “No one was ever going to hand me millions of pounds to direct a film because I was connected to someone of Kate’s stature. I wanted to take the right road, so that I would know when I’d done something it was on my merits and my terms.

“I have proved to myself – and anyone else that may give a shit or not – that I have stuck to the task.”

This he has done with Extraordinary Rendition, a low-budget, intense drama about a Muslim politics lecturer (Omar Berdouni) who is abducted by the CIA from London, flown out of the country, falsely accused of terrorism, interrogated (by the King Kong star Andy Serkis) and tortured. The 1984 for the 9/11 generation, it’s one of the most frightening films you’ll see all year.

“For me, it was about the footsteps we all leave in our lives,” Threapleton says. “Under the wrong kind of microscope even your pattern of international travel can be cause for suspicion.”

Although a fictional portrait – “No one has been lifted from the streets of London, as far as we know” – the film’s authenticity has already been praised by the human rights organisation Amnesty. Everything – from the horrific torture scenes, including the “waterboarding” technique that makes the victim feel as though he’s drowning to Berdouni’s highly committed performance – rings true.

“I remember him saying he felt obligated to get it right,” Threapleton says. “While he could go home every day, wash off the make-up and bathe his bruises away, there are people out there who are not able to do that. That really put things into sharp relief for him.”

Beaten to a theatrical release by the Hollywood Rendition, Threapleton’s movie is bypassing UK cinemas, adopting the same DVD/TV premiere route taken by, among others, Ken Loach’s It’s a Free World. He is under no illusion about the film’s chances in the market-place. “The bare facts for theatre audiences are quite simple: if you’re out on a Saturday night and you’re faced with Knocked Up versus Extraordinary Rendition you’re probably going to go for Knocked Up.”

Not that this was the case in his own family, where politics were debated fiercely over the dinner table. His father was a navigator in the Royal Air Force and “one of my earlier memories is Dad doing a tour of duty in the Falklands, after the war ended. I can’t have been of political debating age [he was born in 1974], but you’re still aware that there are things going on in the world that affect your family.”

It meant a life of moving between military bases for him and his younger brother Rob – who eventually became a helicopter pilot – before they eventually settled in a boarding school in North Yorkshire.

And there is a certain military precision to Threapleton’s life still. Engaged to a school administrator called Julie, he flies out once a month to New York to see his daughter. “There’s a common will between Kate and myself and Sam to protect Mia’s environment,” he says. “Mia is one of the happiest, most confident children I’ve ever come across. And that was down to the will to move on to the next chapter for us all – which is a very happy one, I’m pleased to report.”

Given this very mature attitude, I wonder if they’re at a stage where Threapleton would consider working with his ex-wife. “I can’t foresee that situation arising,” he says. “At the best of times it’s probably a wise thing to keep a distance between friendships, relationships and professional situations.”

Threapleton instead is focusing on a new thriller, Exposure, which he hopes to shoot in June. “It’s satisfying to have a lot of possibilities,” he says. “But we’re still at the start of the road.”

Extraordinary Rendition is released on April 28. It will also be shown at the Frontline Club, London W2 (020-7479 8943) on April 21 (7.30pm), followed by a Q&A with Jim Threapleton

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