Prince Philip became upset with Sarah Ferguson following a series of antics she did while still married to Prince Andrew. Since then, the two royals’ relationship has never been repaired.

In the Channel 5 documentary “The Royal Family At War,” it was revealed that the Duke of Edinburgh was particularly aggrieved after he saw compromising photos of Ferguson with her financial advisor vacationing in St. Tropez. At that time, Ferguson and Prince Andrew have only been separated for five months.

The snap shows Texan millionaire John Bryan seemingly kissing and sucking the Duchess of York’s toes, as well as the arch of her foot. According to royal author Katie Nicholl, up until that point, Ferguson enjoyed warm rapport with Prince Philip. But from that moment on, the 97-year-old retired royal never forgave the mom of two.

Prince Philip became aware that Ferguson caused embarrassment and humiliation to the royal family. The dad of four was also very protective of his wife, Queen Elizabeth II, and he didn’t like anyone to bring the Queen into disrepute.

“She was never welcomed at Balmoral again and she was never welcomed at Christmas with the royal family again,” Nicholl said. “She was an outcast. I think he found Fergie’s antics within the marriage to Prince Andrew one of those difficult royal pills to swallow,” she added.

But several years after the incident, Her Majesty herself decided to extend an olive branch to Ferguson. In 2013, royal author Ingrid Seward said in a documentary that the monarch had always been fond of Ferguson, and they also got along very well.

“So what the Queen used to do, she would invite Fergie up to Balmoral when Philip wasn’t there and then when Philip arrived, Fergie would leave so that their paths would never meet,” Seward said.

Royal correspondent Victoria Arbiter echoed the other experts’ statement by saying that Prince Philip made it clear that he didn’t want to see Fergie. Since Prince Philip was very stubborn and quite set in his ways, the Queen made sure that he would never bump into Ferguson. The two royals only recently crossed paths when they both attended Prince Harry and Meghan Markle’s royal wedding.

Prince Philip Britain's Prince Philip, Duke of Edinburgh, in his role as Captain General, Royal Marines, attends a Parade to mark the finale of the 1664 Global Challenge on the Buckingham Palace Forecourt in central London on August 2, 2017. YUI MOK/AFP/Getty Images