Buckingham Palace issued an unusually direct response to the claims.

Charles Spencer’s memoir about his late sister, Princess Diana, has been published, with revelations about the royal family prompting a rare response from King Charles III.

Swan Song: Diana, My Sister, written by Diana’s younger brother, was published by Penguin on Tuesday and has been translated into 12 languages.

The book comes nearly three decades after Diana died in a car crash in Paris in 1997 at the age of 36. Her life, marriage and death have remained the subject of intense public interest.

Spencer said he wrote the memoir to “speak on Diana’s behalf” and challenge what he described as “untruths that have become accepted over time”.

Extracts from the book were serialised by the Daily Mail in recent days, generating widespread headlines over claims concerning Diana’s relationship with the royal family.

Charles Spencer makes claims about King Charles

According to excerpts published from the memoir, Spencer claims that Charles, who was then Prince of Wales, told him in a telephone conversation shortly after Diana’s death: “Rest assured, we’ll forget her soon enough.”

Spencer also claims that Charles reacted angrily when he argued that Diana would not have wanted her sons, Princes William and Harry, who were 15 and 12 at the time, to walk behind her coffin during her funeral procession.

Buckingham Palace issued an unusually direct response to the claims.

A spokesperson for King Charles said: “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.”

Spencer rejected the suggestion that grief had affected his recollection and insisted that the words attributed to Charles were accurate.

“It is not every day you wake up to find you’ve been gaslit by the king,” Spencer told the Mail on Sunday.

He also criticised the Palace’s response, comparing it with the wording used after claims made by Prince Harry and Meghan about racism within the royal family, when Buckingham Palace said that “recollections may vary”.

Diana’s marriage and personal struggles

Spencer’s memoir also discusses Diana’s difficult marriage to Charles, which lasted from 1981 until their divorce in 1996.

He writes that Diana had at times contemplated suicide and describes an incident in which she drove towards Beachy Head, a notorious clifftop in southern England.

According to Spencer, her love for William and Harry prevented her from going further.

He also recalls Diana telling him that she and Charles were divorcing because Charles was “in love with his valet”. Spencer said he did not question why she believed what he described as an improbable claim.

Charles later married Camilla Parker Bowles, his longtime partner, who is now Queen Camilla.

Royal experts challenge some claims

Some royal commentators have questioned Spencer’s account.

Royal biographer Robert Hardman wrote on X that he had witnessed Charles looking “distraught and in tears” at Diana’s funeral, contradicting Spencer’s description of his reaction to her death.

Andrew Morton, author of Diana: Her True Story, described Spencer’s claim about the alleged telephone conversation as “incendiary and disputed” in a comment published by The Times.

Royal commentator Jennie Bond also described the memoir as a “vindictive account” in an interview with the BBC.

Spencer, 62, has worked as a television journalist in the United States and describes himself as a historian. He inherited the Spencer family’s Althorp estate, where he and Diana grew up. Diana is buried on an island on the estate.

Spencer recalls Diana’s relationship with the media

Following Diana’s death, Spencer accused the media of contributing to the pressure surrounding his sister and delivered an emotional eulogy at her funeral in which he promised to look after her two sons.

His memoir also discusses Diana’s relationship with Dodi Fayed, who died alongside her in the Paris crash. Spencer praised Dodi as someone who had been kind to Diana.

However, he also makes a separate allegation involving Dodi’s father, Mohamed Al-Fayed, claiming Diana had felt strong discomfort around him.

Spencer further told the BBC that the media’s “cancerous influence” on Prince Harry and Meghan reminded him of the intense press scrutiny faced by Diana.

The publication of Swan Song: Diana, My Sister has reopened discussion about Diana’s life, her relationship with the royal family and the continuing differences in accounts of events surrounding her death.