Earl Spencer, the brother of Diana, Princess of Wales, has alleged that King Charles "sounded giddily elated" when he telephoned him following Diana's death in Paris in August 1997.
The claim appears in Spencer's forthcoming memoir, "Swan Song: Diana, My Sister," excerpts of which have been published in the Daily Mail ahead of the book's full release next week.
In the book, Spencer recounts being woken at his home in Cape Town, South Africa, in the early hours of 31 August 1997, by a phone call from his sister Jane alerting him to the car crash. During the calls that followed, the then-Prince Charles telephoned him.
"Unlike my other callers, who were stunned, barely able to articulate their condolences and offers of help, he sounded giddily elated - like a lottery winner, I remember thinking at the time," Spencer writes.
The memoir also alleges that Charles subjected Spencer to a "stream of anger" after Spencer raised objections to Princes William and Harry -- then aged 15 and 12 -- walking in the public funeral procession for their mother on 6 September 1997.
"He unleashed down the phone what I have always taken to be his pent-up contempt for Diana, and his horror that the world was so bowled over by her death. 'Rest assured', he hissed, 'we'll forget her soon enough!'," Spencer writes.
Buckingham Palace strongly rejected the accounts. 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 judgment and colour memory in ways others do not recognise, even many years after such a loss."
According to Spencer, Charles also informed him that he had told Princes William and Harry of their mother's death in their bedrooms at Balmoral. Charles and Diana had divorced in August 1996, more than a year before her death.
Representatives of Prince Harry said they did not wish to comment on the book.
The allegations are the latest in a long-running dispute between the Spencer and Windsor families, which has been a recurring subject in the British press for decades.
Separately, King Charles and Queen Camilla have been based at Balmoral Castle in Scotland for much of September. On Thursday, Charles is scheduled to host executives from artificial intelligence companies including Nvidia, Google DeepMind, OpenAI and Anthropic at Dumfries House in Ayrshire.
"The decisions taken at this formative time will shape the world inherited by future generations," Charles was expected to say, according to excerpts released in advance by the palace. "The task before you is not merely to advance technology, but to ensure that it remains firmly in the service of humanity, community and the natural world."
Britain's Minister for Artificial Intelligence, Kanishka Narayan, and Paolo Benanti, an adviser to Pope Leo XIV, were also expected to attend the event.
