Christopher Nolan has confirmed Sir Michael Caine had a cameo in 'Dunkirk'.

The 'Inception' filmmaker has collaborated with the British actor in six of his films since 2005's 'Batman Begins', his last being 2014's 'Interstellar'.

However, Nolan has now revealed the 84-year-old legend was recorded giving orders to two pilots played by Tom Hardy and Jack Lowden in the World War II epic and he's startled how few managed to place the voice with the actor.

Speaking to, Nolan said: ''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.

''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.''

'Dunkirk' is based on the real-life 1940 British-led rescue mission in which 330,000 Allied troops were rescued from the clutches of the Nazis.

Many of the actors in the film are well-known including Sir Kenneth Branagh and Sir Mark Rylance, others are Nolan regulars such as Cillian Murphy and Hardy, as well as newcomers Fionn Whitehead and One Direction star Harry Styles.

Similar to Caine, Hardy has worked with the director on three movies, 'Inception', 'The Dark Knight Rises' and 'Dunkirk' and recently admitted it would be a ''no-brainer'' if the filmmaker wanted to cast him again, regardless of the scale of the project.

Asked if he'd say yes to anything from the director, Hardy said: ''It's always been that way with Chris, yes. For me, it's wonderful to meet someone who is completely in control of the elements and assets that he has available to him.

''He has a specific confidence that I've not met in another filmmaker. Akin to George Miller actually. Inarritu did as well, actually. They're very specific about what they want.

''But Chris, the most so, out of everyone I've ever worked with. So yeah, it's a no-brainer if he says, 'Tom, do you want to jump on this option?'

''Whatever he wants to do. Even if he wants to shoot a short film in his garden, I know it's going to be good and I'll learn something.''