Diana’s memorial statue will be unveiled in Kensington Palace’s Sunken Garden this week on what would have been the Princess of Wales' 60th birthday. The occasion has been pipped to trigger a genuine reconciliation between her feuding sons, Prince William and Prince Harry, whose rift has only worsened since the Sussexes’ departure from the Firm last year. William and Harry commissioned the statue together on the 20th anniversary of their mother’s death back in 2017, and so were both determined to attend the unveiling ceremony together.

       However, Prince Philip’s funeral in April saw the brothers reunite for the first time in more than a year — only for them to struggle to make any progress in restoring their relationship.

       Still, the brothers were seen chatting after the sombre service in St George’s Chapel — they were very close to their grandfather, and wanted to send him off properly.

       Both Philip and Diana were not only close to the two royal brothers, but the Duke of Edinburgh was said to have been particularly fond of his daughter-in-law.

       They used to write to each other regularly when Diana was in the process of separating from the Prince of Wales.

       Philip said his son was “silly to risk everything with Camilla”, and that “I cannot imagine anyone in their right mind leaving you” for Charles’ then-mistress.

       In one letter, he wrote affectionately: “If invited, I will do my utmost to help you and Charles to the best of my ability.”

       Diana’s reply reads: “Dearest Pa, I was particularly touched by your most recent letter, which proved to me, if I did not already know it, that you really do care.”

       Author Ingrid Seward also claimed: “When [Diana] found the restrictions of royal life difficult, it was Philip who helped her.

       “Once she was married, she never sat next to her husband; she always sat next to Philip at the endless black-tie dinners and he took care of her.”

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       As two outsiders who were suddenly thrust into the spotlight after marrying the heirs to the throne, Philip and Diana were initially able to connect.

       However, their close bond clearly began to sour as Diana’s relationship with Charles worsened and it was clear they were heading for a divorce.

       Writing in her book, ‘Prince Philip Revealed’, Ms Seward said: “The late Diana, Princess of Wales, said he [Philip] was an amusing dinner companion, but she would never look to him for sympathy or go to him for help as opposed to advice or guidance, which he gave her.

       “But at the end of her life she declared she hated him.

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       “In a conversation I had with her on the subject, she informed me she had warned her sons, William and Harry, never to shout at anyone who couldn’t answer back the way their grandfather did.”

       Reportedly, Diana found herself on the receiving end of Philip’s sharp temper once he realised she was having her own affairs and her general behaviour was affecting the Royal Family as a whole.

       Her friend Simon Simmons told the 2008 inquiry into Diana’s death that Philip’s tone towards his daughter-in-law began to change, and recalled how the Princess of Wales shared “two letters that really upset her” from the Duke of Edinburgh.

       Ms Simmons agreed when asked if the letters were “derogatory” towards Diana and added that they were “cruel” and left the Princess of Wales “red in the face”.

       Their letter exchanges in 1994 or 1995 left Diana “absolutely furious” according to Ms Simmons.

       However, Philip gave an official statement acknowledging these letters in 2003, and challenged reports that he had been “insulting” to Diana.

       The statement read: “He [Philip] started the correspondence in June 1992 in a friendly attempt to resolve a number of family issues which arose at the time leading up to the official separation of the Prince and Princess of Wales in December of that year.

       “Prince Philip wishes to make it clear that at no point did he ever use the insulting terms described in the media reports, not that he was curt or unfeeling in what he wrote.”

       Philip has also been credited with taking William and Harry under his wing in the immediate aftermath of Diana’s death.

       ‘Prince Philip Revealed: A Man Of His Century’ by Ingrid Seward was published by Simon & Schuster in 2020 and is available here.