One Direction singer Harry Styles says he congratulated the pregnant Duchess of Cambridge on her "bump" as they met at the Royal Variety Performance.
But Styles added that the royal, who at 16 weeks is nearly halfway through her second pregnancy, "didn\'t look bumpy".
Kate and husband Prince William chatted to the group about their touring plans - with the Duke promising he had been "keeping a close eye" on the young pop stars.
Band member Liam Payne said: "It\'s the most nervous I think I\'ve ever been in my life, while Louis Tomlinson said he feared he had made a serious faux pas.
"I didn\'t say ma\'am," he said, as the royals made their way into the London Palladium. "I said - Hi. How are you? I\'m Louis."
The band was due to take to the stage, along with Bette Midler, Ed Sheeran and the couple\'s wedding singer, Ellie Goulding.
Simply Red, whose frontman Mick Hucknall was one of the favourite artists of William\'s late mother Diana, Princess of Wales, was also due to perform.
Kate, who wore a black Diane von Furstenburg gown at the theatre, returned to royal duties in late October after her extreme morning sickness - known as hyperemesis gravidarum - showed improvement.
The Queen and Prince Philip have traditionally attended the Royal Variety Performance but this year William and Kate were there for the first time.
The Duke and Duchess of Cambridge attended their first Royal Variety Performance at the London Palladium
In future, it is thought the Cambridges will take it in turns with the Prince of Wales and the Duchess of Cornwall, who went in 2013.
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