Princess Diana’s only brother has revealed where he stands on the infamous rift between her sons, Princes William and Harry.

“I think there is a perception in the media that I am on Harry’s side. Well, I’m on my deceased sister’s sons’ side, both of them,” Charles Spencer told the BBC in an interview released on Sunday (British time) to mark the publication this week of his new book, Swan Song: Diana, My Sister.

“If either of them wanted anything, then I’d be equally there for them. And I never get involved in one camp or the other, except as a benign figure, I hope.”

Earl Spencer told the BBC there were a “lot of reasons on both sides” for the brothers’ relationship having “got to this stage”.

“I hope one day it’s resolved,” he said.

“But I don’t know all. I certainly don’t know what’s been done in the finer detail and so I would feel intrusive if I got more involved than to say of course a mother would want her two sons to be happy together and love each other.”

Diana died aged 36 in a 1997 Paris car crash as photographers pursued her on motorbikes.

Her death sparked an outpouring of grief and a ‌reckoning over whether the media bore some responsibility after years of splashing details of the princess’s life across front pages.

Spencer’s book – which is highly critical of Diana’s former husband, the now-King Charles – follows the return of Prince Harry and his wife Meghan Markle to live in Britain, six years after they quit royal duties and moved to the US.

The so-called “Megxit” contributed to the breakdown of Harry and William’s relationship.

The Duke of Sussex has also spoken out about his family in his own memoir, Spare, and a hit Netflix TV series. The Prince of Wales, meanwhile, has said nothing public about the relationship in years.

But the brothers, remembered by many for walking side by side behind their mother’s coffin at her 1997 funeral, are reportedly estranged and have not spoken in years.

Harry and Meghan’s return to Britain last month has also reignited controversy over their lack of taxpayer-funded protection.

It was stripped when the couple quit as working royals and moved to North America. The prince has fought an ongoing – and so far unsuccessful – battle to have it restored and the decision is now under review.

Spencer told the BBC that the Sussexes should have some official security.

“From a security aspect, as an uncle who’s seen his sister die in very, very preventable circumstances, I would veer towards protection,” ‌he said, citing Harry’s position as ⁠fifth-in-line to the British throne and as a former soldier.

Spencer said the tabloid treatment of both Diana, and ​Harry and Meghan, could be “really, really unpleasant”, that it was “beholden on people” to learn from that experience.

Spencer’s book has already made headlines around the world. The earl has accused the then-Prince of Wales, of sounding “giddily elated” in the hours after Diana’s death. He said an angry prince told him the world would forget Diana soon enough.

Buckingham Palace hit back in a rare public rebuke, saying the King was “mindful that the ‌pain of fraternal ​grief can cloud reason, affect judgment and colour memory in ways others do not recognise, even many years after such a loss”.

Asked by the BBC how he could ​prove the conversations ‌that he claimed, Spencer said he had included a specific line in his much-lauded eulogy at Diana’s funeral to counter the comments, ending it by saying she ​would “never be extinguished from our minds”.

Spencer said he had written the book, ahead of the 30th anniversary of Diana’s death, to celebrate her life. He said their childhood had never had a dull moment.

“We both have ADHD. She was never diagnosed, but clearly we did,” he said.

Spencer said his revelations would not come as a surprise ​to the princes.

“I don’t like to talk about what I’ve been speaking about to William and Harry but this will not be a surprise to them, I will tell you that. These words will not be a surprise to them,” he said.

The earl said he knew many more details about the King but had chosen not to ​include them in the upcoming book.

-with AAP