Let the games begin!

Kate Middleton, hubby Prince William and brother-in-law Prince Harry were front and center outside Buckingham Palace on Thursday afternoon among the throngs to greet the Olympic torch.

After a charity sporting event earlier in the day, the Duchess of Cambridge, 30, changed out of a belted Hobbs "Wessex" dress into casual, sporty gear for the momentous occasion -- a fitted white Olympic polo shirt plus skinny, bright-blue denim.

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Flanked by William, 30, and Harry, 27, the Duchess grinned and applauded as the final torchbearer lit a cauldron, according to BBC News.

The trio showed off their own athletic skills Thursday morning at the launch of Coach Core (a sports coaching initiative for 16-19-year-olds), where the Duchess (a lacrosse champ at school) played ping pong and later kicked off her Pied-a-Terre wedges to referee a judo match.

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Joked William in his remarks at the event: "Watching me on the football [soccer] field is never a pretty sight -- the expression 'giraffe on ice' springs to mind. . . .Catherine, on the other hand, with a tennis racquet or a hockey stick is something to behold and be aware of."

This article originally appeared on Usmagazine.com: Kate Middleton, Princes William and Harry Cheer at Olympic Torch Rally!