Filmmaker Christopher Nolan says he felt "an enormous responsibility" while making his new film Dunkirk.

The film is based on the Dunkirk evacuation in 1940, and Nolan says he had a lot of responsibility while making something about real-life events.

"There's an enormous responsibility that comes with it. And that sense of responsibility - particularly for a British person working in what's really sacred ground in British culture -- when you then come to screen the film, all of that responsibility, all of that pressure comes flooding back," Nolan said.

"We had a screening for the veterans that I had spoken to, their families. Honestly, never felt quite such pressure in a professional setting as standing in front of that audience and about to show our version of what they'd actually lived through," he added.

Dunkirk, which released in India on Friday, features Fionn Whitehead, Harry Styles, Mark Rylance and Tom Hardy.