It was a celebration fit for a princess duchess! Prince William had just the ticket (or tickets, judging by their party posse) for Kate Middleton's 31st birthday, as the royals, along with Pippa, James, Carole and Michael Middleton, and a handful of Kate's close personal friends, hit up London's Royal Albert Hall to check out the Cirque du Soleil production of Kooza. E! has exclusively obtained photos of their jubilant gang—check them out!
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