Prince William Missed Diana on His Wedding Day
05/29/2012 AT 11:15 AM EDT
"Very difficult" is how the prince recalls her absence that day, as he reveals during an ABC interview airing Tuesday night, as part of The Jubilee Queen with Katie Couric.
"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," says William, 29. "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."
Diana was killed in a Paris car crash in August 1997, when William was 15.
"I think she ... she would have loved the day and I think, hopefully, she'd be very proud," he tells Couric. "I'm just very sad that she's never going to get a chance to meet Kate."
Prince Harry, 27, also gets a chance to remark on his brother's wedding day and what it would have meant to their mother.
"I think she had the best seat in the house, probably," says Harry. "But yeah, she would have loved to have been there."