The ever-gracious Colin Firth turns serious when he discusses his big-screen portrayal of a British soldier tormented by memories of the harrowing conditions endured as a forced labourer during the Second World War.
The Oscar-winning actor says dramatizing the true story of Eric Lomax in The Railway Man was made all the more significant because of the input the film had from the veteran himself.
"I haven't had any experience which is equivalent of this," Firth said while discussing the movie, which premiered at the Toronto International Film Festival.
"You feel a responsibility to be as truthful as you can. It's not a straightforward thing to fulfill because we're not following the facts exactly as they were, we're not following the details exactly as they were because it's impossible. This is a story that unfolds over 50 years, 70 years now, and we have 90 minutes."
The film is based on Lomax's own experiences, which the soldier detailed in a book as a therapeutic exercise.
The veteran, who died last year, faced gruelling conditions building the Thailand Death Railway after being captured by Japanese troops. His traumatic experiences continue to haunt him years later and it was only the intervention of his wife – played by Nicole Kidman – that helped him move toward recovery.
The film follows Patti Lomax's search for her husband's torturer, which culminates in victim and abuser finally meeting years after the war that has shaped them.
Depicting with accuracy the endurance and tremendous humanity soldiers like Eric Lomax displayed came with a "huge amount of pressure," said Firth.
"If the characters you're playing, if they exist and you form a personal relationship with them, it becomes personal. It's no longer just the case of a job to be done," he said.
"This is a long storytelling process … it's on behalf of an awful lot of people who weren't able to speak out, that didn't have a voice and that still haven't been heard."
Firth noted, however, that bringing Lomax's true story to wider audiences was not a burden.
"There's something about being trusted that's motivating as well," he said
"You just want to be absolutely sure that you don't drop the baton, that you don't compromise how well this story has been told up to now."