Although Prince William appears to have a friendly relationship with Queen Elizabeth, a royal biographer claims the Duke of Cambridge has not forgotten the way his grandmother treated Princess Diana during her divorce from Prince Charles.

When the couple announced their separation in 1992, their split became front-page news. After the estranged husband and wife shared details about their crumbling marriage and affairs in revealing interviews, Queen Elizabeth ordered the pair to get a divorce.

In the book, “Harry: Conversations with the Prince,” Angela Levin revealed that one of the conditions of the divorce stripped Princess Diana of her title, Her Royal Highness. “Diana could also retain the title of Princess of Wales but could no longer be called Her Royal Highness, a title that shows that the individual has a direct family connection to the crown and assures they will be automatically included in state occasions, which Diana was not,” she explained.

Although Prince Charles reportedly demanded Diana give up her HRH title, in the 2007 biography “The Diana Chronicles,” Tina Brown claimed that Queen Elizabeth ultimately decided to strip her daughter-in-law of the royal title.

“Who knew where Diana’s private life might take her in her second act and what kind of unforeseen difficulties might be caused by some ghastly second husband?” Brown wrote.

“The Queen was never going to let Diana keep the title,” she added.

Levin later revealed that Prince William remains unhappy about the way Queen Elizabeth forced his mother to give up her title and her marriage. “William has never accepted this snub,” the royal biographer wrote.

In the book, “A Royal Duty,” Princess Diana’s former butler, Paul Burrell, claimed Prince William was his mother’s main support system during her divorce negotiations. The Princess of Wales was reportedly distraught when she learned she would be stripped of her HRH title.

Burrell claimed that although William was just a boy, he did his best to comfort his mother. “She told me how he had sat with her one night when she was upset over the loss of HRH, put his arms around her and said, ‘Don’t worry, Mummy. I will give it back to you one day when I am king,’” Burrell wrote.

When the divorce was finalized, Princess Diana was given a £17 million lump sum and £400,000 per year. However, following her death in 1997, the money went into a trust for Prince William and Prince Harry.

Queen Elizabeth and Prince William
Queen Elizabeth II worried about Prince William. The Duke of Cambridge is pictured during “The Patron’s Lunch” celebrations for The Queen’s 90th birthday on June 12, 2016 in London, England. Jeff Spicer/Getty Images