The royal couple, first-timers at the event, stole the show when they stepped on stage at the London Palladium.
Kate, who is 16 weeks pregnant with her second child, was glowing in a floor-length black lace Diane von Furstenburg gown. She wore her hair in an elegant chignon offset by diamond drop earrings.
The merest hint of a bump was on show as she and husband William did the rounds, greeting performers including boy band hybrid McBusted – made up of members of McFly and Busted – and Ellie Goulding.
“I’d find it pretty hard to walk around a circle and pretend that you like everyone, and they do it very, very well,” Ed Sheeran joked after meeting the royal couple.
“But yeah, they’re really, really friendly.”
The royals were welcomed to the historic venue by Andrew Lloyd Webber and wife Madeleine Gurdon, before meeting members of One Direction.
“It’s the most nervous I think I’ve ever been in my life,” Liam Payne said.
But Harry Styles appeared unfazed by his brush with royalty, offering the Duke and Duchess his best wishes for their growing family.
“I said congratulations on the bump,” he said later – though he added that “she didn’t look bumpy”.
William revealed he is a big Bette Midler fan, gushing after the show that it was the first time he had seen her perform and that she was “amazing”.
Bette, who curtseyed when she met the Duchess, has already announced plans to play North America in 2015, in what will be her first major tour in a decade.
Among all the stars, there were some friendly faces.
Kate had a chance to reminisce with an old schoolmate, comedian Jack Whitehall, before heading off stage.
“It was lovely,” Jack said. “We had a little catch-up about school. It wasn’t that in-depth. It was like a school reunion, with just me and her.”
There were big laughs from the audience earlier in the evening when he joked that his mother was disappointed he had not snapped up the former Ms Middleton when he had the chance.
“She’ll be doing it tonight, she’ll be watching the Royal Variety show and I know what she’ll be saying – she’ll be like, ‘Oh look, there he is, the black sheep of the family, embarrassing himself in front of the one that got away’.”
William and Kate have had a number of engagements this month after the Duchess returned to royal duties in late October after her extreme morning sickness – known as hyperemesis gravidarum – showed improvement.
Traditionally, the Queen has taken it in turns with the Prince of Wales to attend the show, and it had been expected to be the monarch who would be seated in the royal box this year, but William and Kate’s attendance is a demonstration of how the younger members of the family are stepping in to help the Queen, who turns 89 next year. It is thought the Cambridges will take it in turns with the Prince of Wales in future.
“As with any other invitation, attendance by the Queen and the Duke of Edinburgh will be assessed on a case-by-case basis,” a Buckingham Palace spokesman said.
Charles and the Duchess of Cornwall watched the performance last year, while the Queen and the Duke of Edinburgh last went in the Diamond Jubilee year of 2012.
The event is held in aid of the Entertainment Artistes’ Benevolent Fund, of which the Queen is patron.
The show will be screened on ITV in December.
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