A teenage Prince William made a heartrending vow to his mother Diana just one year before her untimely death in the French capital.

The 21st anniversary of the car crash that took her life is approaching, and Diana’s butler Paul Burrell revealed in his book A Royal Duty that her eldest son William had vowed to give back her HRH title when he became king.

Diana

The Princess of Wales was stripped of the style when she divorced Prince Charles, becoming Diana, Princess of Wales. But at the time, 14-year-old William told his mother, “Don’t worry Mummy, I will give it back to you one day when I am king,” leaving her in tears.

Tragically, he never got to fulfil his promise, as Diana’s fatal car accident happened just a year later in Paris on 31 August 1997, ending her life at the age of just 36.

Loyal sons

Princes William and Harry have always praised their mother for pushing boundaries. William recently applauded her 1995 BBC Panorama interview where she opened up about her relationship with Prince Charles and said there were ‘three people’ in their marriage.

He said, “I can understand – having sometimes been in those situations, you feel incredibly desperate and it is very unfair that things are being said that are untrue. The easiest thing to do is just to say or go to the media yourself. Open that door. [But] once you’ve opened it you can never close it again.”

Cruelly stripped of her title

It was thought Diana would be allowed to keep her HRH title when she and Charles divorced, but that didn’t happen. The couple married in 1981, but their relationship is thought to have been under strain just four years later, and they divorced in 1996.

The terms of the divorce stripped Diana of her title and she became Diana, Princess of Wales – meaning she would have to curtsey to Charles, who married Camilla Parker-Bowles in 2005, and their sons William and Harry. Clearly upset, William made the promise to Diana when he was studying at Eton College near Windsor, and he intends to keep to his word if and when he becomes king.

Keeping her memory alive

William and his wife Kate, both 36, have ensured that Diana’s memory would live on. The prince used his mother’s oval sapphire and diamond engagement ring to propose to Kate in 2010 and their wedding paid several tributes to the late princess.

When Kate walked out of the Lindo Wing of St Mary’s Hospital in London after giving birth to both of their sons, Princes George and Louis, Kate wore similar dresses to the ones Diana wore when she left the same hospital with William and Harry. The couple’s daughter, Princess Charlotte, is also named after her late grandmother – her full name is Charlotte Elizabeth Diana.

Prince Harry, 33, and his wife Meghan, 37, also honoured Diana at their wedding in May. They chose her favourite flowers, white peonies and white garden roses, to decorate the archway at St George’s Chapel, and Harry picked another of her favourites, forget-me-nots, for Meghan’s bouquet.

We have no doubt that Diana would be incredibly proud of William and Harry.