Diana, who died aged 36 following a Paris car crash in 1997, lost her Her Royal Highness designation after divorcing Charles, now 77, the previous year.
A royal source claimed William has remained deeply affected by the decision and views restoring his mother’s status as a profoundly personal ambition.
The insider added the prince had never forgotten the significance of Diana losing her HRH designation and regarded reversing that decision as a “meaningful way of honoring her.”
But the source claimed William is “reluctant to turn the anniversary into a competition with Harry, who has discussed the possibility of producing a documentary examining their mother’s life and legacy.
“William favors a permanent, understated tribute over a television production or elaborate public commemoration. The proposed restoration would also fulfill a longstanding claim that William promised Diana, while still a child, that he would reinstate her royal style when he became monarch.
“But he knows it will enrage Charles, so he is said to be waiting until after his father passes to make the move.”