The 23-year-old made a dapper appearance on the red carpet, forgoing his usual quirky style for a smart and simple black suit with a white shirt.
Prince Harry asked the then long-haired Styles: "When was the last time you had a haircut?"
Styles has been winning rave reviews from publications who have seen Dunkirk - including Metro.co.uk who reckon he's got a solid film career ahead of him if he wants it.
Styles makes his acting debut in the World War II movie, which explored the evacuation of Allied soldiers from Dunkirk, France. Though Nolan helmed the "Dark Knight" trilogy, the 46-year-old director suggested his franchise days are behind him.
"While another was left furious that his no show ruined their day, tweeting: "#ThisMorning I WOKE UP AT 5AM TO RECORD HARRY'S INTERVIEW AND IT WAS ONLY 5 MINUTES LONG I PROPOSE A PROTEST".
He said: 'I don't think I was that aware of how famous Harry was. "I've never quite understood why a modern film hasn't been made about it and, as a filmmaker, those are the kind of gaps that you're looking to fill".