The former X Factor contestants who are now international superstars are set to perform for Duchess Kate and her husband Prince William at tonight's show. William and Kate have both previously admitted to enjoying the ITV reality show.
Both Harry Styles and Duchess Kate looked happy to meet one another at the Royal Variety Performance
Prince William reportedly told the boy that he had been "keeping a close eye" on them, and Harry's bandmate Liam Payne added: "It's the most nervous I think I've ever been in my life."
Louis Tomlinson said he feared he had made a serious error, revealing: "I didn't say ma'am. I said - Hi. How are you? I'm Louis."
The royal couple arrived earlier in the evening looking happy and ready for a fun night ahead with the Prince keeping close to pregnant Kate, who looked gorgeous in a long black gown with full-length lace sleeves by Diane Von Furstenberg.
Prince William and Harry Styles shake hands at the Royal Variety Performance
As well as One Direction, Ed, and Ellie performing, the star-studded show will be hosted by award winning comedian Michael McIntyre while Russell Kane, Jake Whitehall, Sarah Millican and Trevor Noah will be providing the stand-up comedy.
The programme will air on ITV in December, and is a staple of the Christmas TV season in Britain. It has been running for over 100 years and is always attended by members of the British royal family.