Christopher Nolan revealed that legendary actor Michael Caine made a cameo in Dunkirk, and he is shocked that a lot of people have not noticed his presence.

Dunkirk, featuring Tom Hardy, Harry Styles and Cillian Murphy in the lead, released last week.

Nolan says Caine lent his voice to a scene featuring Hardy and Jack Lowden. "It's shocking to me that a lot of people haven't (spotted the cameo), when he has really one of the most distinctive voices in cinema," he says.

"I wanted very much to squeeze him in here. It's a bit of a nod to his character in Battle of Britain. And also, it's Michael. He has to be in all my films, after all," he adds.

Caine has featured in all of Nolan's films since Batman Begins in 2005. In Dunkirk, he can be heard giving orders to pilots Hardy and Jack Lowden in the cockpit.