Kate Middleton celebrates her birthday at London showing of Cirque du Soleil

Kate Middleton celebrated her 31st birthday with Prince William and her family on Wednesday at a London performance by Cirque du Soleil.

Middleton, Prince William, her sister Pippa Middleton, brother James Middleton, and parents Carole and Michael Middleton attended Cirque du Soleil's Kooza show at London's Royal Albert Hall, located just across the street from her home at Kensington Palace, reports E! News.

She was seen laughing, clapping, gasping, pulling her hair across her face and curling into William, since the show is tense. And according to People, an observer reports she was looking "happy and radiant."

There was even a clown onstage who had his crown stolen at one point during the show and pointed into the crowd, asking, "Who has my crown?" Middleton and her mother burst into laughter and glanced over at William, who laughed along with them.

Aside from her family, Middleton was also joined by her friend Sophie Carter, cousins Lucy and Adam Middleton, friends Teddy Foyle and David Jardine-Paterson, and Kate's old schoolmates Trini Foyle and Emilia Jardine-Paterson. Some security was there as well.

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