Prince William vowed to give Princess Diana her royal title back once he becomes king

Prince William had only spent a limited time with her mother Princess Diana due to the divorce and her untimely demise.

However, despite the physical distance, the Duke of Cambridge was quite close to the Princess of Wales and had even made a special promise to her.

After Diana and Prince Charles’s divorce, the princess’s Her Royal Highness (HRH) title was stripped as per her ex-husband’s insistence, even though Queen Elizabeth II had no objections about her keeping it.

This meant that Diana had to curtsy to all members of the British royal family, including her sons Prince William and Prince Harry.

Diana’s butler, Paul Burrell revealed the promise that 14-year-old William made to his mom in his book, A Royal Duty.

Burrell wrote that Diana was promised by William to have her royal title back when he takes over the throne.

"Don't worry, Mummy, I will give it back to you one day when I am king,” Burrell quoted William.