As Princess Diana was about to split from Prince Charles, her father-in-law Prince Phillip extended support to her during those tumultuous times.
The pair often exchanged caring letters as reported by Woman & Home, in which Philip would sign off as Pa.
Prince Philip wrote to Princess Diana on July 7 1992: "I can only repeat what I have said before. If invited, I will always do my utmost to help you and Charles to the best of my ability. But I am quite ready to concede that I have no talent as a marriage counsellor!"
In reply, Diana expressed being grateful for the advice, referring him in the letter as Pa.
"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," she wrote.
"You are very modest about your marriage guidance skills, and I disagree with you! The last letter of yours showed great understanding and tact, and I hope to be able to draw on your advice in the months ahead, whatever they may bring."