Buckingham Palace has strongly disputed a claim by Earl Spencer that King Charles III told him Princess Diana would soon be forgotten following her death in 1997.

Spencer, Diana’s younger brother, made the allegation in his forthcoming memoir, Swan Song: Diana, My Sister, recounting a heated conversation with Charles in the aftermath of Diana’s death in a Paris car crash.

According to an excerpt published by the Daily Mail, Spencer said Charles became angry after he objected to Princes William and Harry, then aged 15 and 12 respectively, walking behind their mother’s coffin during her funeral.

Spencer alleged that Charles expressed what he described as long-held contempt for Diana before telling him: “Rest assured, we’ll forget her soon enough.”

Buckingham Palace rejected the account, issuing an unusually strong statement while stopping short of explicitly describing Spencer’s version as untrue.

The Palace 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.”

The wording has been compared with a statement issued by Queen Elizabeth II in 2021 following claims made by Prince Harry and Meghan Markle, when she said that “recollections may vary.”

Julian Payne, a former communications secretary to Charles, also questioned the account, saying the alleged remark was not language he recognised as characteristic of the King.

Payne described the Palace’s decision to respond as highly unusual, indicating the strength of feeling surrounding the allegation.

Diana died in a car crash in Paris in August 1997, triggering widespread public mourning and renewed scrutiny of the Royal Family’s relationship with the Princess and its response to the public reaction to her death.

Spencer’s emotional address at Diana’s funeral became one of the most notable moments of the aftermath.

His memoir, which is scheduled for publication next week, revisits his relationship with Diana and events surrounding her death, including his account of the disagreement over the role of William and Harry in the funeral procession.

The dispute comes as members of the Royal Family undertake several public engagements.

Charles is scheduled to host senior artificial intelligence industry figures at Dumfries House in Ayrshire, where he is expected to discuss the rapid development of AI, its potential effects on society and the need for the technology to be safe and beneficial to humanity.

AI Minister Kanishka Narayan and representatives of OpenAI, Anthropic, Nvidia and Google DeepMind are expected to attend.

Meanwhile, Prince William and Catherine, Princess of Wales, are visiting the Isle of Bute, where they are scheduled to participate in community and volunteering activities, watch a game of shinty, visit a community-owned pub and meet groups involved in environmental conservation.

Prince Harry is also due to attend the first Invictus Awards ceremony in the UK, which will honour people associated with the Invictus Games and celebrate their resilience and service.

It remains unclear whether Meghan Markle will accompany him. The couple are expected to continue their UK activities as private citizens rather than as working members of the Royal Family.