It's no secret that Prince Philip is the most strong-willed member of the British royal family, and his low opinion of a certain royal following a humiliating scandal has remained consistent over the years.
The feud dates back to 1992, when Fergie was separated from the Duke of York and was pursuing a relationship with her financial adviser, John Bryan.
Peoplereported that following her separation from Andrew, Fergie "packed their bags for a 36-day tour of Thailand and Indonesia, a five-day jaunt to Argentina, a spree in Paris and a journey to Scotland."
Despite being joined by her daughters who were aged four and two, she was also accompanied by her then-lover John Bryan.
During the famous trip, Fergie was scandalously photographed topless in the South of France whilst Bryan sucked her toes.
In other photos, the couple appeared to be kissing while her daughter, Princess Eugenie, looked on.
When the photos surfaced a few days later, the Duchess of York was with the Royal Family at Balmoral in Scotland - essentially the lion's den.
Royal correspondent James Whitaker told Express that "It happened in front of the whole family at the Queen’s country residence in Scotland."
"She was late into breakfast and everybody had got a copy of the Daily Mirror.
"As she walked into the room, they all stuffed it under their Times and Telegraphs and that sort of thing.
"She knew the game was up the second she walked into the room."
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Writing in her autobiography years later, Fergie described the moment where the members of the royal family found out about the photos.
"It would be accurate to report that the porridge was getting cold. Eyes wide and mouths ajar, the adults were flipping through theDaily Mirror," she said.
While Sarah and Andrew had officially separated, they had also been seen together at Royal Ascot and had made public appearances alongside each other that year.
According to reports, the Queen had invited Fergie to Balmoral at that time discuss "her future."
Though Fergie's relationship with her father-in-law was allegedly never rosy to begin with, the controversy was the one thing needed to destroy her relationship with him altogether.
According toExpress, Prince Philip is said to be the coldest towards Fergie, but Queen Elizabeth also took issue with the scandal.
"The Queen was furious, absolutely furious. I think partly because she loved Fergie so much," Ingrid Seward, editor ofMajesty magazine once said.
"She just couldn’t believe Fergie could have been so stupid to allow this to happen."
On the day the photos surfaced, her Majesty reportedly asked the mother-of-two to leave the Balmoral estate.
Prince Philip no longer speaks to Sarah Ferguson - the ex-wife of his son Prince Andrew and mother of his grandchildren, Princess Beatrice and Princess Eugenie.
The publication also reported that the Queen and Prince Philip are still taking measures to avoid their son's ex-wife.
After Fergie and Prince Andrew separated, Buckingham Palace announced that the former Duchess of York would no longer carry out public engagements on behalf of theQueen.
Furthermore, her Majesty announced that she would not be taking responsibility for her former daughter-in-law's debts.