Prince Harry says he only cried once at Diana's funeral: 'Two people who were most loved by her were unable to show any emotion'

It was an event that shook the world, but those at the centre of it were numb, Prince Harry reveals, as he recalls only ever crying once after Princess Diana's death in 1997.

A preview for his upcoming interview with Tom Bradby for ITV has Harry revealing his thoughts during his mother's highly-publicised funeral, held weeks shy of his 13th birthday.

"I cried once, at the burial, and you know I go into detail [in his memoir, Spare] about how strange it was and how actually there was some guilt that I felt, and I think William felt as well, by walking around the outside of Kensington Palace," he told Bradby.

Watch the video above.

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"There were 50,000 bouquets of flowers to our mother and there we were shaking people's hands, smiling... And the wet hands that we were shaking, we couldn't understand why their hands were wet, but it was all the tears that they were wiping away," he continues.

"Everyone thought and felt like they knew our mum, and the two closest people to her, the two most loved people by her, were unable to show any emotion in that moment," he pointed out.

Spare reportedly focuses on how his mother's loss shaped him throughout his years, especially with the dynamic in the royal family, with his older brother Prince William being the "heir" to his "spare".

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Royal expert Russell Myers says that in that clip alone, it can be seen that Harry is a "troubled man".

"I got a sense of sadness watching that clip and I imagined the interviews he's taking part in, which will be aired over the next few days, will show that that he is a very, very troubled man," he said Today this morning. Show this morning.

"He carries this burden of the death of his mother so heavily and you're talking over a quarter of a century ago, and it still seems like it was last week for him. It's particularly sad for him."

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Harry also says Diana would also be "sad" at seeing the rift between him and his brother.

In a teaser for an interview with Good Morning America, Harry told host Michael Strahan, "I think she would be looking at it long term to know that there are certain things we need to go through to be able to heal the relationship."

Spare is set to be released in Australia on January 11, but according to The Sun, was reportedly accidentally put on sale five days early in Spain. Members of the public were briefly able to pick up copies of En La Sombra, which translates to "In the Shadow", before the books were quickly pulled.

As for Harry's pre-launch interviews for Spare, which are set to contain more allegations against the British royal family, UK's ITV will be airing their sit-down interview first on Sunday at 9pm (8am Monday AEDT).

This will be followed by CBS' 60 Minutes in the US at 7.30pm Sunday local time (11.30am Monday AEDT) and ABC's Good Morning America on Monday morning local time, followed by CBS' The Late Show With Stephen Colbert on Tuesday night local time, which is Wednesday afternoon Australia time.

The British royal family are understood to not be commenting on any allegations made by Harry in the memoir.