Nearly three decades after Princess Diana's death, her brother has plunged the British monarchy into an unusually public war of words. Charles Spencer's new memoir, Swan Song: Diana, My Sister, accuses King Charles III of coldness bordering on cruelty toward his late sister — and Buckingham Palace's rare public pushback has only escalated the fight, dragging in broadcaster Piers Morgan, who is now threatening to sue.

In the book, published this week by Michael Joseph, an imprint of Penguin Random House, Spencer recounts a furious 1997 argument with the then-Prince of Wales over funeral arrangements, alleging Charles "went ballistic" when Spencer objected to 15-year-old William and 12-year-old Harry walking behind their mother's coffin, and snapped: "Rest assured, we'll forget her soon enough." Spencer also writes that Charles sounded "giddily elated" on the phone after learning of Diana's death, and that Diana herself had tried to call off their engagement after discovering he had bought a bracelet for Camilla Parker Bowles.

A rare palace rebuke

Buckingham Palace, which as a rule does not comment on books, broke with that practice to respond directly. "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 palace said in a statement. Spencer did not let the implication — that grief had distorted his memory — go unanswered. "It is not every day you wake up to find you've been gaslit by the king," he told the BBC, calling the palace's response "astonishingly provocative and below the belt." He has said Princes William and Harry were shown his claims before publication.

"It is not every day you wake up to find you've been gaslit by the king." — Charles Spencer, 9th Earl Spencer

The row has since widened. Spencer issued a public apology Wednesday after acknowledging he had "got a date wrong" in a passage accusing Piers Morgan of helping publish "stolen" paparazzi images of Diana while at the Daily Mirror — Morgan did not actually join the paper until nearly two years after those photos ran. Morgan has demanded Penguin pull the book from shelves, arguing: "If Earl Spencer can be so incredibly, defamatorily wrong about basic facts involving me, why should we believe anything else he puts in this book?" Spencer says future print runs and e-book editions will be corrected, but he is refusing to withdraw the first edition, maintaining his broader account of Morgan's "surly behaviour" around Diana's funeral still stands.

The dispute lands the royal family in another round of unwelcome headlines, coming just months after the fallout from the Prince Andrew scandal and amid the still-unhealed rift between William, Harry and their father. For now, neither William nor Harry has commented publicly on their uncle's allegations. Spencer, for his part, has hinted there is more he has not yet made public, telling interviewers he is holding back additional material about the King. With the book newly on shelves in twelve languages and a legal threat from Morgan hanging over its publisher, the question now is whether Buckingham Palace — or Prince William — responds further, or lets the war of words burn itself out.