If Christopher Nolan, 46, may have regretted his decision to cast Styles after Dunkirk’s set was invaded by hoards of One Directioners then today he is more than satisfied with the young pop star’s performance.

“The proof of the pudding is in the eating,” says the director. “People can finally get to see what Harry has done now and I think his performance is really marvellous.”

Styles can now add his name alongside Leonardo DiCaprio, Tom Hardy and Christian Bale and the other illustrious A-listers who have populated Nolan’s films, Interstellar, Inception or the Dark Knight trilogy.

As a director, Nolan insists he never worries too much about people’s history or reputation. “I always come back to when I cast Heath Ledger as the Joker. There was a lot of raised eyebrows; a lot of like why? How’s that going to work?

“But my job as a director is to see potential in people who haven’t done a thing before – whether you’re talking about a movie star or a first-timer or a pop star, for example when I cast David Bowie in Prestige [2006]; if I see a thing that can work there, I can’t worry too much about the baggage.”

Co-star Fionn Whitehead concurs: “I can vouch for the fact that there were no egos involved in the making of the film, everyone was really there because they wanted to be there – Harry included.”

Dunkirk hits cinemas this Thursday.