Former One Direction star Harry Styles says he found shooting Dunkirk physically tough.

The 23-year-old singer makes his acting debut in director Christopher Nolan's upcoming wartime saga and loved working on the ambitious film, reported RollingStone.

“The movie is so ambitious. Some of the stuff they're doing in this movie is insane. And it was hard, man, physically really tough, but I love acting.

“I love playing someone else. I'd sleep really well at night, then get up and continue drowning,” Styles says.