The 29-year-old heir to the throne of England said in an interview for ABC's "The Jubilee Queen with Katie Couric" special that Diana's absence from his special day was "very difficult."
"I sort of prepared myself beforehand so that I was sort of mentally prepared. ... I didn't want any wobbly lips or anything going on," the prince said.
"It's the one time since she's died, where I've ... thought to myself it would be fantastic if she was here, and just how sad, really for her more than anything, not being able to see it," he said. "She would have loved the day and I think, hopefully, she'd be very proud. I'm just very sad that she's never going to get a chance to meet Kate."
Couric's special, which focuses on the 60th year of Queen Elizabeth II's reign, is to air on ABC Tuesday night.