Director Mark Herman switched from British working-class dramas, to the Holocaust with the Boy In Striped Pyjamas. Not everyone was pleased.

It was back in the summer of 2005 that Mark Herman, the Yorkshire-born writer/director, read an advance proof of a debut novel by Irish writer, John Boyne, called The Boy In The Striped Pyjamas. Set during the Second World War, the novel told the story of an improbable friendship between Bruno, the naïve eight-year-old German son of a Nazi commandant posted to run Auschwitz-Birkenau, and Shmuel, a Jewish boy of the same age, imprisoned in the camp.

Herman sneaked an early look at the book because he and Boyne were represented by the same talent agency. He was fascinated by the novel's child's-eye depiction of the moral impact on the wife and children of a high-ranking Nazi who come to realise what atrocities their husband and father is overseeing mere metres from their front door.

"What really attracted me was that it felt like a unique angle," says the 54-year-old director, whose previous work includes British hits Brassed Off, Purely Belter and Little Voice. "Obviously a child's point of view is not quite new, but I thought a German childhood point of view was a really interesting angle to take."

He tentatively enquired about film rights, sure they would have long since sold. "I was a bit surprised that no studio had already snapped them up," he says, speaking from his home in Yorkshire. "Although obviously I think the subject matter is probably quite off-putting."

He considered the potential pitfalls of a non-Jewish director pitching a non-Jewish writer's unpublished novel to the studios and concluded that it would float best if he presented it as a ready-to-go screenplay.

"I thought if a studio could read a screenplay rather than a book then they might get the picture a bit more, so I stuck my neck out and bought the film rights for a while and wrote away."

By the end of 2005, he had finished a rough draft of the screenplay and attracted the interest of, first, Miramax and then producer David Heyman, the mastermind behind the Harry Potter film franchise.

With financing in place, Herman, with Boyne's approval, set about changing elements of the book to smooth its transition to film. "There are various things about the book, such as it being set in Auschwitz and Hitler visiting the commandant, those things that are real, I wanted to take out, because if we're saying this is Auschwitz, then David Thewlis [who stars as the Commandant] is playing a specific character and I was very keen to keep it a fictional story. The kids meeting at the fence, this is the story."

By the time Herman was bringing in these changes, the novel had been published and become a runaway success (to date, it has sold three million copies and been widely translated), putting Herman in safe commercial territory.

At the same time, he was delving ever deeper into researching the Holocaust. "Most research now takes place on the internet and you'd just find yourself on sites you shouldn't be on and that actually became a bit distressing. And everybody in every department did that in the end, they'd all gone through this period of researching the subject to a such an extent that it actually began to affect them."

Considering the novel is set at Auschwitz-Birkenau, it is surprising that Herman never visited the camp as part of his research. "I didn't visit Auschwitz. But I intended to go just before we started shooting."

Filming began on location in Hungary on the anniversary of Hitler's death ("a coincidence", says Herman) in 2007 and wrapped later that summer.

First reactions to the finished work inevitably focus on similar issues that faced John Boyne, namely: can a non-Jewish artist depict the events of the Holocaust with the necessary insight and sensitivity?

"I hear that," admits Herman. "And I also hear: ‘Don't write about it unless you were there', that kind of thing. But if that was the case, there'd be very few films made and very books written."

He has also been criticised for presenting what some consider to be a misleading depiction of life in a concentration camp such as Auschwitz. Throughout the film, the boys' friendship flourishes on the understanding that Shmuel can come and go as he pleases within the camp and freely spend time by an unguarded fence chatting with the camp commandant's son on a daily basis. Liberties like these have never appeared in any account of life in the camps. Such fits of artistic licence underscore concerns that some younger viewers will come away from the film believing camps like Auschwitz to have been less barbaric than the documented reality.

And then there is also the matter of Shmuel's relatively robust appearance throughout the film, another focus for criticism. "A lot of people say how healthy people look [in the camp scenes] and my sort of argument is, there's a scene early on where they're being rounded up and taken out of Berlin and nobody's complaining about how well or full-bodied they look then. But the final scene in the film is only two or three weeks later.

Our perception of the Holocaust is usually from the final days. Everybody expects any scene in any Holocaust film to be full of skeletal people and this takes place quite early on, so there's no real reason for them to be quite as emaciated. Plus, Shmuel himself has only just arrived."

Conversely, the film has also earned rave reviews, for its deft positioning of childhood naïveté amid unthinkable evil. What kind of reactions has Herman had to date from Jewish viewers? "So far very, very supportive. It's a subject that perhaps the studio were apprehensive about and I think what has happened has been very interesting. There's been a very positive reaction."

Next month, the film is set to premiere in Israel. Does Herman expect audiences to be moved? "I think so," he says. "Though you don't know what to expect. But touch wood, so far wherever we've been apprehensive, it's been really well received."

With much talk these days of how best to keep reminding the world of the tragedy of the Holocaust, does Herman envisage his film becoming an educational tool? "We're of a generation now where you want to start a new generation on keeping the story going and always going and I think this film is a very good introduction for kids into it."

The Boy in the Striped Pyjamas opens on September 12