King Charles responds to claims in Earl Spencer's book about Princess Diana

King Charles lll has taken the rare step of commenting on the content of Earl Spencer's upcoming book about the late Princess Diana.

On Wednesday, the Daily Mail published the first preview of Swan Song: Diana, My Sister, the memoir by Charles, 9th Earl Spencer, the brother of the late Princess of Wales, set for release on 22 September.

In the book, Spencer recounts a phone conversation with the then Prince Charles after Diana's death on 31 August 1997. Spencer wrote of the heated exchange, "Prince Charles continued his stream of anger, without me interrupting. Then he stopped.

"I assumed the pause signalled an effort to bring himself under control, but then 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.'"

A statement from a palace spokesperson released shortly after the story went live read, "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."

Swan Song: Diana, My Sister was announced last month. The book marks the first time Spencer has spoken at length about his late sister, and he noted he was inspired to write it after being inundated with requests for interviews as the 30th anniversary of Diana's death approaches.

"The aim of this book is to tell the truth about Diana from her brother's perspective," Spencer shared in a press release.