Prince Harry says he only cried once after Princess Diana died and felt 'guilt' for smiling on a walkabout outside Kensington Palace following her fatal crash

• Prince Harry is reflecting on his experience of mourning Princess Diana in public in 1997.
• In a promo clip for his ITV interview on Sunday, Harry said he felt "guilt" for smiling in public.

Prince Harry only cried once after Princess Diana died in 1997 and said he felt guilty for smiling in public after the tragedy.

In a promo clip for his upcoming ITV interview with Tom Bradby, the Duke of Sussex shared a glimpse of what the experience of mourning his mother in public was like. Harry was 12 when Diana was killed in a car accident in Paris, France on August 31, 1997 aged 36.

Recalling the aftermath of his mother's death, Harry told Bradby that he remembers that time of his life as being "strange," adding that he elaborates in detail in his memoir "Spare," set to be released on Tuesday.

"Everyone knows where they were and what they were doing the night my mother died," he said. "I cried once at the burial and, you know, I go into detail about how strange it was."

What's more, Harry said that he also experienced feelings of guilt for how he appeared in public in the days following his mother's death.

After Diana died, he and Prince William, then 15, met members of the public in front of Kensington Palace and viewed the thousands of floral tributes left in their mother's honor.

"Actually there was some guilt that I felt, and I think William felt as well, by walking around the outside of Kensington Palace," Harry said. "There were 50,000 bouquets of flowers to our mother and there we were shaking people's hands, smiling."

ITV overlaid the interview with footage of Harry and William outside Kensington Palace that shows them smiling and talking to people mourning Diana.

"I've looked back over it all, and the wet hands that we were shaking but it was all the tears that they were wiping away," he said.

"Everyone thought and felt like they knew our mom," Harry added. "And the two closest people to her, the two most loved by her were unable to show any emotion at that moment."

According to the BBC, Harry goes into depth in "Spare" about his attempts to seek closure following Diana's death. It reported that Harry wrote about asking a driver to take him through the tunnel in Paris where his mother's car accident occurred in hopes that it would bring to a close a "decade of unrelenting pain."

More details will be shared in the Duke of Sussex's four upcoming broadcast interviews. ITV's interview promoting "Spare" is set to air in the UK at 9 p.m, while a separate interview with Anderson Cooper for 60 Minutes on CBS is also airing on Sunday at 7:30 p.m ET.

Harry will also be interviewed on ABC's Good Morning America with Michael Strahan on Monday and on The Late Show with Stephen Colbert on CBS on Tuesday.