Britain's Prince William and Prince Harry each recalled Tuesday how much they missed their late mother, Princess Diana, on William's wedding day last year.

"It was very difficult," William, 29, told Katie Couric on ABC News' "The Jubilee Queen," a special devoted to his grandmother Queen Elizabeth II's 60th year on the throne, which aired Tuesday night.

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"It's the one time since she's died where I've thought to myself it would be fantastic if she was here." The prince added that his mother would have "loved the day and I think, hopefully, she'd [have been] very proud of us both for the day."

Prince William also mentioned how much he regretted that Diana -- who died in a car crash in Paris in August 1997, when he was 15 -- is "never going to get a chance to meet Kate" Middleton, his bride.

Still, said his brother, Harry, 27, "I think she had the best seat in the house, probably. But yeah, she would have loved to have been there."

Also Tuesday, Kate, the Duchess of Cambridge, attended her first Buckingham Palace garden tea party, which attracted 8,000 guests. The British paper The Daily Telegraph quoted the Duchess as saying at the event, "It's very nerve-racking facing such a sea of people, but great fun." Queen Elizabeth, Prince Philip, Prince Charles and his wife, Camilla, the Duchess of Cornwall, also attended the event. The garden party is a traditional highlight of the London spring-summer season.