Inside Buckingham Palace there is a sense of crisis once again after the latest blow to the King’s reign, this time delivered by the late Princess Diana’s brother Earl Spencer.

Palace officials are privately questioning Spencer’s motives for writing the explosive new memoir, asking “is it just about money?”.

Royal sources say Charles III, who has suffered his fair share of turmoil in four years on the throne, is furious that his former brother-in-law has targeted him in the book, Swan Song: Diana, My Sister.

Spencer’s claims threaten to revive years of controversy about Diana’s life and death.

They also risk undermining a long and successful campaign to rehabilitate the 77-year-old monarch’s reputation and ensure that his second wife, Camilla, has been accepted by the British public.

The feud with Spencer could also threaten the King and Harry’s efforts to repairs rifts. However, a source close to Harry told The i Paper: “He was aware of the book, but not its content.”

‘Is it just about money?’

Spencer, 62, has attempted to justify the book by arguing that he wanted to set the record straight about some “untruths” told about his late sister.

But Palace officials have privately questioned this. “Why now? Is it just about money?” one asked. “What does he hope to gain by doing this?”

Courtiers, asked if the King is considering suing Charles Spencer or planning a briefing war to trash his reputation, insist for now that a statement issued within 90 minutes of the first extract dropping on the website on Wednesday will be the extent of his public response.

“We won’t be adding to it,” one palace official said.

But there may be more yet that the King wants to counter. The Palace is braced for further revelations in the Mail’s serialisation and when journalists on other titles start pouring over the book after it is published next Tuesday.

Although it is hard to imagine anything more damaging than Spencer’s claim that in the days after Diana’s death in 1997, the then Prince Charles told him: “Rest assured, we’ll forget her soon enough.”

It was a comment that appeared so incredibly callous, even in the midst of a heated row in the aftermath of a shocking family death, that the King, breaking with his usual practice of trying to hold the line and say nothing unless it becomes absolutely necessary, issued an immediate denial on Wednesday evening.

The response echoed the late Queen’s famous “recollections may vary” retort to Harry and Meghan’s Oprah Winfrey television interview in March 2021. A Palace spokesman said: “While we do not comment on books as a matter of principle, His Majesty is 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.”

Spencer has already begun to give interviews, telling the BBC he is “telling the truth” about his claim that the King told him Diana would be forgotten “soon enough” following her death.

“Those are exactly the words he said,” Spencer told the broadcaster. There is also unconfirmed speculation that he may do further interviews, including with one of the main US networks to help launch the book in the States next week.

There have been further revelations since the first claims, including that Charles, the then Prince of Wales, sounded “giddily elated” after Diana’s death, amid speculation from Spencer that he was pleased because it paved the way for him to marry the woman he loved, Camilla.

The author is said not to have shared the contents of the book with Charles or the King’s sons, Prince William and Prince Harry, who have each found this week that the controversy has overshadowed their work.

On Thursday, Charles was convening a meeting of industry experts from around the world to try to devise a framework for developing artificial intelligence amid fears it could become so powerful it could kill all human life in the next 10 years.

However, for most of the day the media and public’s attention was focused on the sensational claims about his reaction when died in a Paris car crash in 1997.

The feud with Spencer also threatens the King and Harry’s efforts to rebuild trust and repair rifts created by the Duke and Duchess of Sussex’s exit from official royal duties six years ago.

Harry, who celebrated his 42nd birthday on Tuesday, has remained uncharacteristically silent about his uncle’s explosive book. In public, at least, he is not taking sides.

But he, Meghan and their children stayed with Spencer at the ancestral home, Althorp, in Northamptonshire in July. It seems incredible that the subject of the forthcoming tome would not have come up in conversation.

The Page Six column, rarely sympathetic toward the Sussexes, insisted they did discuss it at Althorp. One insider reportedly said: “It didn’t come as a shock.”

But a source close to Harry told The i Paper: “He was aware of the book but not its content.”

In his own memoir, , Harry recounted his uncle’s objections to Diana’s two boys having to walk behind her coffin in the funeral procession, and appeared to support Spencer’s celebrated attack on the Royal Family in his eulogy at her funeral.

“Truth hurts,” Harry wrote, describing his father’s anguished reaction.

Spencer’s wider criticism of the Royal Family’s treatment of Diana tallies with some of his own grievances about the monarchy and his efforts to break free from the institution’s gilded cage.

Some in royal circles think they see the pair working together to pursue an agenda in the run-up to the 30th anniversary, in August next year, of Diana’s death.

“I do not trust young Harry’s motive at all. I wouldn’t be surprised if the Sussexes end up living in a house on the Althorp estate,” one old friend of both the Royal Family and the Spencer family said, questioning whether at the root of it all lay one common factor: “Dosh.”

After their move across the Atlantic from California, the Sussexes are already not too far from Althorp.

Harry has made it clear that seeing the Spencer side of his family is just as important to him as reconnecting with his father and the Windsors.

And if reconciliation with the latter fails, that would not be a reason to quit Britain again, according to that source close to them, who said: “Their relationship with the Royal Family, I don’t think is likely to influence where they want to live.”

A spokesperson for the Sussexes cast doubt on the idea that they might move to Althorp, saying it was “the first I’ve heard of that”.

Royal relationships on the line

Harry has been approached about taking part in several documentaries to mark the 30th anniversary of his mother’s death. But so far, he has not decided whether to take part, or if he wants to make his own film, according to the same source.

At the same time, Harry has sounded conciliatory towards his royal relatives. He has rationalised much of his anger and frustration at his treatment by blaming the institution and the “men in grey suits” – the courtiers advising the family – rather than his father and late grandmother.

It may also have irked him that Uncle Charles chose to sell the serialisation rights for his book to the after its huge court victory over Harry and six other famous people. The group collectively now face a legal bill of up to £34.5m after losing a privacy case against the newspaper group.

With royal relationships and the reputation of the King all in play, the stakes are high. Could Charles have said something so cruel in grief, shock and anger during a row with Spencer over whether his boys should walk behind Diana’s coffin?

Many who know Charles well insist he pushed to give her a royal funeral rather than one for a private individual. He was anxious that nobody in his household spoke ill of her after her death.

A family friend concurred but also recalled the vicious briefings against Diana from Charles’s camp during the War of the Waleses before her death.

The Spencers, she said, were always fuming, but the then Prince of Wales was no angel.

“King Charles threw the most dreadful temper tantrums,” she said. “He also said some very strange things at times.”

The controversy, and the prospect of more revelations in the run-up to the 30th anniversary, is yet another distraction for the monarchy alongside Andrew and Epstein, the Sussexes’ return, and other scandals.

But, in spite of it all, royal aides and other insiders believe the institution is resilient enough to survive and thrive.

“It won’t wreck the King’s reign,” one courtier said.