But it was that evening, at the red-carpet BAFTA dinner, where the royals set Hollywood's own royalty on its heels, mingling with, and wowing, the likes of Tom Hanks, Jennifer Lopez, Nicole Kidman and Barbra Streisand. About 42 emerging British actors also attended, along with such Hollywood up-and-comers as Ed Westwick, Blake Lively and Chris Evans.
"They're the biggest stars in the world," CNN host, and fellow Brit, Piers Morgan noted of Kate and William's appeal. "You tell me, who's gotten married in the history of Hollywood who had 2 billion people watching."
Prince William (who's also the president of BAFTA) delivered a speech at the gala, which spotlighted emerging British talent and building partnerships between Hollywood and up-and-coming British actors.
But it was Prince William's new bride, Kate, who stole the show once again with a stunning entrance on the couple's first Hollywood red carpet, wearing earrings loaned by the queen, Jimmy Choo sandals and a lavender gown by Alexander McQueen, the same fashion house that designed her wedding gown.
Kate's wardrobe, rumored to be 40 outfits in all for a trip in which she changed as many as three or four times a day, could have been the most watched, and most anticipated, aspect of the couple's first official trip overseas.
"She's making a mark in the fashion world, for sure," celebrity stylist Rachel Zoe told ABC. "She's flawless. Whatever she wears sells out in minutes."
SEE PHOTOS: Kate Middleton's Best Fashion Moments
The duchess, as was widely reported, chose to travel without a stylist or royal dresser on this trip, part of the young royals' "trimmed down" entourage, but she still dazzled heads and hearts with her fashion choices.
She brought mostly feminine looks, including a pleated lilac floor-length gown designed by Sarah Burton of Alexander McQueen, a vibrant green dress and handbag by American designer Diane Von Furstenberg and a silver silk dress with hand-painted flowers by British designer Jenny Packham.
"That is just effortless at its best," Zoe said of Kate's style. "She really looks like she just goes into her closet and says, 'I'm going to put on jeans, a cute pair of shoes and go out the door and, oh yes, I'm a princess.'"
"No matter what she wears, it's going to be on trend, it's going to stay," Zoe said.
On Sunday, before heading back to the U.K., Kate chose an outfit that allowed her to be perfectly at ease as she visited with children, wearing a navy and white crochet top and a white pleat skirt, both from not a fashion house but U.K. High Street brand Whistles, and sapphire and diamond earrings to complement her famous sapphire engagement ring.
The Associated Press contributed to this story.