Harry Styles has admitted he had no idea what part he was auditioning for when he tried out for Dunkirk.

The One Direction star makes his acting debut in Christopher Nolan’s movie about the evacuation of French beaches in 1940.

He plays Alex, one of the junior soldiers desperately trying to get home as the enemy forces close in, but did not know that when he first read for the part with the film’s eventual star, Fionn Whitehead.

Styles told the Press Association: “We auditioned together and I was sitting in a cold, lonely room and Fionn came in from a set of something he was working on and there was one other person in there.

“You had no idea what part you were auditioning for. We didn’t know how many parts there were and they kind of round robin-ed us a little bit, so we did everyone with everyone.”

Styles with the rest of the Dunkirk cast, as well as director Christopher Nolan and producer Emma Thomas (Ian West/PA)

As a newcomer to film sets, Styles said his first day on location in Dunkirk with director Nolan was “pretty overwhelming”.

He added: “I think as much as you can imagine what something like that is going to look like, people don’t make that.

“I don’t know in what other situation someone gets to do what he did so he was pretty amazing to be around.

Christopher Nolan and Emma Thomas
Christopher Nolan with producer Emma Thomas (Ian West/PA)

“You are kind of in awe of it a lot of the time, just continuously during the film.

“At times the tide would go out and you could see ruins of some of the old boats that were out there and it was moments like that when everyone was aware of how special the place that we were was.”

Styles said he had been a fan of Nolan since his 2000 film Memento, starring Guy Pearce.

He said: “I think I always found his structure so interesting and in terms of the way he keeps stuff from the audience when the characters don’t know about it and it hits you so much harder.

“You always feel like you’re right alongside the character, rather than watching a film of stuff happening to them.”

Styles’s Hollywood debut has been highly anticipated, with fans of the singer flocking to the film’s locations to see him in action, but he is not sure he will act again.

He said: “I might be one and done. I think I’m one and done, to be honest. I think so.”

Dunkirk is released in UK cinemas on July 21.