Richard Kay, a close friend of the late Princess Diana, has voiced his confusion regarding a particular anecdote included in Earl Spencer's new memoir, "Swan Song: Diana, My Sister." Kay, who knew Diana both personally and professionally, described the passage as "mystifying" and questioned the Earl's intentions in sharing it.

The memoir, which has been serialized in the Daily Mail, includes claims that have drawn a rare statement from Buckingham Palace. Earl Spencer alleged that King Charles III, then Prince of Wales, told him, "Rest assured, we'll forget her soon enough!" during discussions about Diana's funeral arrangements. A Palace spokesperson responded that while they do not comment on books, His Majesty is "mindful that the pain of fraternal grief can cloud reason, affect judgment and colour memory."

However, the anecdote that has particularly puzzled Kay occurred during a period when Diana's marriage was reportedly deteriorating. According to the memoir, Diana confided in her brother, whom she called "Carlos," at her favorite restaurant, San Lorenzo. "Carlos, I'm going to get a divorce," she said. When Spencer advised her to think carefully, warning that the public might turn against her, Diana allegedly replied, "Carlos, he's in love with his valet."

Kay noted that the anecdote is presented without context or further explanation in the book. The Earl's sister never named the valet, and Spencer himself stated in the memoir that he never asked for clarification on the "improbable thing."

"I have to say, I'm mystified why he should need to use that anecdote," Kay said during an appearance on the Daily Mail's "Palace Confidential." "They're going to ask, was it true? But I think the main question they're going to have, and I'm afraid it's one I really don't have an answer for, is why did he put it in there?"

Kay suggested that the inclusion of the anecdote might be motivated by a desire for retribution, stating, "My only view is that Charles Spencer, to use that rather well-worn cliché about revenge being a dish best served cold, decided to put it in for that reason."

Earl Spencer has defended the inclusion of the exchange, telling the BBC that it occurred within the context of a conversation where Diana was expressing that her marriage was over. The memoir is set for publication tomorrow.