EXCLUSIVE: King Charles 'Fearing Charles Spencer Evidence Trail' Amid Book Row

King Charles is "fearing an evidence trail" behind Charles Spencer's explosive Princess Diana memoir after Buckingham Palace took the extraordinary step of publicly challenging his recollection of events, royal sources have told RadarOnline.com.

Spencer, 62, has triggered a fierce royal row with Swan Song: Diana, My Sister, published this week ahead of the 30th anniversary of Diana's death.

The historian has made a series of contentious claims about Charles, 77, including that the then-Prince of Wales said "we'll forget her soon enough" during a dispute following Diana's fatal 1997 car crash.

Buckingham Palace has strongly questioned Spencer's recollection.

A royal source has now claimed, "The concern for the King is that Charles Spencer isn't simply presenting himself as somebody recalling conversations from three decades ago. He's an historian who understands the importance of records, contemporaneous conversations and establishing a chronology.

"That potentially makes this more complicated than simply saying two people remember an extraordinarily traumatic week differently. The Palace has already questioned his memory publicly, so anything Spencer can produce that supports elements of his account inevitably becomes significant.

"There is some regret that responding before publication may have elevated the confrontation. The Palace largely refused to engage with (Prince) Harry's Spare, but this time it challenged Spencer directly – and he immediately came back fighting."

The insider noted, "Nobody knows what material Spencer retained or precisely what he recorded at the time. But he says he discussed the alleged conversation with friends and relatives because it shocked him so deeply. That creates the possibility of other people being drawn into an argument the Palace would rather leave in the past.

"The difficulty is that Spencer has also now acknowledged making at least one mistake elsewhere in the book. That gives his critics ammunition, while he remains adamant that his central recollections involving the King are accurate. It has become a battle over credibility, and the evidence trail Spencer may have on Charles has the king full of fear at this point."

Spencer claims Charles sounded "giddily elated" after Diana died, and has alleged that Palace officials wanted Prince William and Prince Harry to walk behind their mother's coffin partly to protect their father from possible public hostility.

Buckingham Palace responded unusually forcefully, saying "the pain of fraternal grief can cloud reason, affect judgment and colour memory in ways others do not recognise."

Spencer accused the Palace of "gaslighting" him, with many comparing its language to the late Queen Elizabeth II's famous "recollections may vary" response to Harry and his wife Meghan Markle's infamous Oprah Winfrey TV interview.

Spencer has insisted his account of the disputed conversation is accurate, saying: "I can tell you here and now, those are exactly the words (Charles) said."

But controversy over the memoir intensified after broadcaster Piers Morgan, 61, threatened legal action over a separate passage.

Spencer apologized for incorrectly assuming Morgan had been responsible for publishing intrusive photographs of Diana during the 1990s.

A spokesman said: "As an historian, accuracy is important to Earl Spencer. He therefore wishes to clarify that his assumption was incorrect. Earl Spencer apologises to Mr Morgan for this error."