PIC: Prince William, Kate “Let Loose” at Star-Packed Polo Match

Prince William and Kate Middleton
 John Shearer/Getty Images

Game on!

The Duke and Duchess of Cambridge arrived (via helicopter) at the Santa Barbara Polo and Racquet Club on Saturday afternoon for the day's first official event of the royal tour of Southern California: The Foundation Polo Challenge.

Duchess Kate, 29, made her U.S. sporting debut in a "De Gournay" silver and marble gray hand-painted chinoiserie silk dress by Brit designer Jenny Packham. Her husband Prince William, also 29, looked preppy-handsome in a white polo, white pants and a blue blazer. See more pics of the royals from the polo match.

And Kate was feeling playful about her latest sartorial choice. When one attendee asked who she was wearing, she had a quick retort: "I'm sure you know by now."

Raising funds for the American Friends of the Foundation of Prince William and Prince Harry (a U.S. branch of the royals' charity, which serves at-risk youth, war vets and their families and environmental causes), the Polo Foundation Challenge features William himself among its players — and plenty of Hollywood celebs watching in the stands.

Joe Jonas, Rob Lowe, Rosario Dawson, Alex Pettyfer, Rosie-Huntington Whiteley, Orlando Bloom, Jennifer Love-Hewitt and Zoe Saldana are among the attendees for the event, where the Duchess will hand out the trophy to the winner. Celeb chef Giada de Laurentis prepped the lunch for the affair.

Prince William shared more of his wit in his opening remarks. "In terms of coming back, that depends on the result out there today," he quipped to the crowd. "I'm not a good loser."

"It has to be one of the most beautiful polo grounds anywhere in the world," he said of the club. "My father, The Prince of Wales, and my brother, Harry, were as green as that grass outside when I told them I’d be here today."

"Catherine and I have had a busy few days," he added of their whirlwind Canadian tour. "So the prospect of being able to let loose this afternoon is wonderful for me. But that's what sport is all about – be it polo or football, sorry, I mean soccer or whatever your preferred sport is, more specifically how sport helps young people to find purpose in life – is a key element to the Foundation that Catherine, Harry and I have established."

For access to all our exclusive celebrity videos and interviews – Subscribe on YouTube!