Harry says royals out to undermine Spare

The Duke of Sussex has denied boasting about killing 25 Taliban while serving as a soldier and claimed members of his family are in an active campaign to "undermine" his book.

Harry appeared on The Late Show with Stephen Colbert on Tuesday night in the United States and shared jokes about feeling like he was in "group therapy", the empty seat next to him being "the spare" and his "todger".

There were also some more serious moments, in which he said he believed he had seen his mother Diana, Princess of Wales a "handful of times" after her death and claimed the British press were "abusing" his wife before they left the United Kingdom.

The duke said writing his book, Spare, was the "most vulnerable I have ever been in my life" before adding "I've never felt stronger".

Harry said he most remembers his late grandmother the Queen for her "sharp wit" and sense of humour and that he was "grateful" his grandparents did not have to go through the "global suffering that everybody's experienced over the last three years".

Harry sat down for the interview to a standing ovation from the audience, as he joked the two chairs in front of him were "the chair and the spare".

The duke quickly used the prime-time CBS show to criticise the British press for leaks of his book.

"They intentionally chose to strip away all the context and take out individual segments of my life, my story and every experience I've had, and turned it into a salacious headline," he said.

Protests were sparked by Spare, which on Tuesday became the UK's fastest-selling non-fiction book, due to Harry writing he had engaged in "the taking of human lives" while serving as a helicopter pilot in Afghanistan.

"So, my number is 25. It's not a number that fills me with satisfaction, but nor does it embarrass me," he wrote.

Harry, 38, told Colbert it had been "hurtful and challenging" watching the reactions following the book's publication.

"Without a doubt, the most dangerous lie that they have told is that I somehow boasted about the number of people that I killed in Afghanistan," he said.

Harry said he was driven to discuss his kills by the goal of reducing veteran suicides.

"I made a choice to share it because having spent nearly two decades working with veterans all around the world, I think the most important thing is to be honest and to give space to others to be able to share their experiences without any shame," he told Colbert.

"And my whole goal, my attempt with sharing that detail, is to reduce the number of suicides."

Colbert asked the duke if he believed there was an "active campaign by the rest of your family, by the royal house ... to undermine this book".

"Of course, mainly by the British press," Harry said.

Asked again if it was "aided and abetted by the palace", Harry replied, "yes, again, of course - this is the other side of the story".

In another part of the interview, the duke said he believed press and public fascination with him and his wife was a way to make Meghan Markle leave the UK and to "break her".

Toward the end of the interview, Harry was questioned about his trip to the North Pole where his penis was frost-nipped.

"Can I have a drink?" Harry said, before asking "how long have you been waiting to ask that question".

"We've taken quite a leap from grief and trauma to my todger," he said.

Harry then appeared to use an expletive bleeped out by the show when describing a piece of equipment he did not have on his expedition to the North Pole.

The Late Show interview caps off Harry's press run for his headline-grabbing autobiography, which has sold 400,000 hardback, e-book and audio format copies.