Royal aides have reportedly been holding discussions over whether they can prevent Prince Harry publishing his memoir.
Palace staff are said to be deeply concerned that the book, which is due to go to print before the end of the year, may contain damaging revelations about the Royal Family.
There have been reports that the Duke of Sussex is attempting to negotiate for the book to be toned down following the death of the Queen and his subsequent temporary truce with brother Prince William.
The Prince of Wales invited Harry and wife Meghan Markle to join him and Kate Middleton for a walkabout in Windsor days after the Queen died.
The siblings stood shoulder to shoulder during several solemn processions on the day of their grandmother's funeral, as well as joining their royal cousins for a vigil around her coffin.
However, royal sources previously said there is still "a serious amount of distrust in the air" between the brothers with their relationship still hanging in the balance until the contents of Harry's book are revealed.
The Daily Mail reports that the latest talks are part of a presidential-style strategy aimed at ensuring the crucial first 100 days of the King's reign go smoothly.
A friend of the King is quoted as saying: “The question inside the Palace is: 'Can the book be stopped?'
“It may be that even Harry can’t stop it at this stage but the feeling at the very top is that there’s no good that can come of airing grievances in public.”
Should the book be released, royal lawyers from the firm Harbottle and Lewis are expected to be on standby to read the memoirs.
However the King is unlikely to seek a legal battle with his own son, who may be unable to prevent or amend the book given his £36 million deal with Penguin Random House.
Assuming the book is released on schedule before Christmas, it will be published at an important moment in King Charles III's reign.
A Palace source added: “His Majesty will build on the points he has expressed to the nation: now that the period of mourning is over, he will support diversity, promote community spirit and protect the space for those with faith and those without.
“He is mindful that, as King, his interests and passions will continue but that… some of his previous commitments will now continue in the trusted hands of others.”
