The world's biggest boyband met the most famous royal couple in London on Thursday night (13Nov14) when One Direction came face to face with the Duke and Duchess of Cambridge at the annual Royal Variety Performance.

The pregnant Duchess, who wore a black Diane von Furstenburg lace gown to the big gig, chuckled as she spoke to heartthrob Harry Styles.

He later told reporters he had congratulated Prince William and his wife "on the bump", adding, "She didn't look bumpy".

Bandmate Liam Payne confessed he was overcome with nerves as William chatted to him about the group's tour plans, revealing he has been following One Direction's success online.

And Louis Tomlinson feared he'd shattered official protocol by forgetting to call the royal couple by its titles: "I didn't say ma'am. I said, 'Hi, how are you? I'm Louis'."

After their royal meeting, One Direction took the stage and performed alongside Bette Midler, Ed Sheeran, Simply Red and Ellie Goulding, who performed at the Duke and Duchess' wedding reception.