They became so close during the course of their nearly 30-year friendship that she was known as “and also” on account of her name always appearing on the Duke of Edinburgh’s guest list.
So it was hardly a surprise when the Countess Mountbatten of Burma was included in the 30-strong congregation for Prince Philip’s funeral, handpicked by the Queen.
Also known as Penny Knatchbull, later Lady Romsey and Lady Brabourne, the 68-year-old mother of three was the Duke’s carriage driving partner and one of his closest confidantes.
Yet it emerged on Saturday that the Countess, pictured below, was actually representing her husband, the Earl of Mountbatten of Burma, who is unwell and therefore unable to attend.
Lord Brabourne, 73, who is godfather to the Duke of Cambridge, was too ill to walk his daughter, the Honorable Alexandra Knatchbull, down the aisle in 2016, leaving the honours to Prince Charles.
The British peer is the grandson of former Admiral of the Fleet Lord Louis Mountbatten, the 1st Earl of Burma, a British Royal Navy officer and statesman who was Prince Philip’s Uncle.
The former Viceroy of India and chief of the defence staff acted as a mentor to Prince Charles, who referred to him affectionately as Uncle Dickie, when he was growing up.
The Royal family was left devastated when he was killed by an IRA bomb, planted on his fishing boat in Mullaghmore, County Sligo, in August 1979.
Prince William is understood to have named his youngest child Louis after him.