King Charles considered Queen Camilla 'non-negotiable' after Princess Diana, author claims

For King Charles, Queen Camilla was never up for debate — she was "non-negotiable."

The claim comes from British author Catherine Mayer's new book, "Divide & Rule," which explores history's most misunderstood royal wives ahead of Queen Camilla's July 17 birthday.

A spokesperson for Buckingham Palace told Fox News Digital they don’t comment on books.

ROYAL FAMILY FACES BACKLASH FROM CRITICS AFTER QUEEN CAMILLA HOSTS J.K. ROWLING

According to Mayer, multiple anonymous...