EXCLUSIVE: Prince William 'Beyond Furious' Over Charles Spencer's Princess Diana Memoir

Prince William is "beyond furious" over Earl Spencer's explosive Princess Diana memoir, royal sources have told RadarOnline.com, as the prince faces another examination of his mother's death nearly three decades later.

The Prince of Wales, 44, is said to be upset by Swan Song: Diana, My Sister, in which his uncle Charles Spencer, 62, makes claims about King Charles, 77, and the aftermath of Diana's death at age 36 in Paris in 1997.

Kensington Palace has not commented on William's reaction, while Buckingham Palace has taken the unusual step of challenging Spencer's account.

A royal source claimed: "William is beyond furious that all of this has been dragged into public again. For him, this is not ancient royal history or material for another book – it is his mother, his father and the most traumatic period of his childhood.

"He has spent years wanting Diana's memory treated with dignity rather than endlessly turned into fresh controversy. The fact that these allegations are now coming from his own uncle makes the situation particularly painful."

The insider noted, "William understands that Charles Spencer has his own memories and his own relationship with Diana. But there is a feeling that publishing claims this incendiary inevitably forces William and Harry back into events they experienced as grieving children, which has led William to become beyond furious over its release.

"The timing has also caused huge anger. The 30th anniversary of Diana's death is approaching, and instead of allowing her sons to remember her privately, another battle has erupted over who said what during that terrible week."

Spencer's memoir alleges the then-Prince Charles told him during an argument over Diana's funeral arrangements: "Rest assured, we'll forget her soon enough."

He also claims Charles sounded "giddily elated – like a lottery winner" after learning of Diana's death.

Buckingham Palace has challenged Spencer's recollections, issuing a rare response after extracts appeared.

A spokesperson 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 judgement and colour memory in ways others do not recognise, even many years after such a loss."

The dispute has resonance for William because Diana is buried on an island at Althorp, Spencer's Northamptonshire estate, where the prince can visit his mother's resting place.

It also comes as Prince Harry, 42, has developed a closer relationship with Spencer.

Sources have claimed Harry knew his uncle was writing the memoir, although there is no evidence he knew its detailed contents before publication.

At the center of Spencer's account is the argument over whether William, then 15, and Harry, then 12, should walk behind Diana's coffin during her funeral procession.

Spencer said he opposed the idea, while Charles allegedly insisted the boys should participate.

William and Harry ultimately walked behind their mother's coffin alongside their father, grandfather Prince Philip, and Spencer.

Julian Payne, Charles' former communications secretary, has questioned Spencer's account of the King's alleged remark.

Payne told the BBC: "(Charles) was very clear that there was never to be any criticism, never to be any pushback on the narratives that were usually highly critical of him – but he was absolutely emphatic that we were to respect her memory and not undermine it in any way.

"It seems to me very odd that in the moment itself, with the grief of his family and his own shock, that he would choose that moment to use those words."

"It's just not language that I recognize," he added.

Swan Song: Diana, My Sister is due to be published worldwide on September 22.