Sarah and Philip had already bonded over a shared raucous sense of humour and, to the senior royal, her rather boisterous approach was a refreshing change to the personal dramas of Princess Diana. It was clear who was his favourite daughter-in-law.
Within a year of her marriage, when she became the Duchess of York, Sarah’s lavish spending and penchant for the high life soon earned her the nickname “Freeloading Fergie”.
But it was her close-to-the-mark sense of fun that pushed it too far for Philip, when, claims the Kitty Kelley book The Royals, she was seen impersonating him by goosestepping around a room like a Nazi stormtrooper.
Philip’s Nazi connections – three of his sisters were married to Germans who had ties to Hitler – have long been a source of embarrassment to a man who served with distinction in World War II.
And so the tide began to turn. As her marriage to Andrew began to crumble, there was also talk of Sarah having affairs with beaus like Texas millionaire Steve Wyatt.
“Philip became more and more irritated with Fergie and what he described as her ‘antics’,” royal biographer Ingrid Seward claimed in the book Prince Philip Revealed. “He began to take every opportunity to criticise her.”
The turning point came one day when Sarah, tired of Philip repeatedly picking on Andrew, stood up for him, demanding the attacks stop.
“It was the death-knell for their relationship,” Ingrid says. “Philip simply doesn’t like being challenged by someone he considers his intellectual inferior.”
The brewing squall turned into a raging storm in 1992, when the estranged Andrew and Sarah divorced.
WATCH BELOW: Fergie announces her first romance novel. Story continues after video...
In August, Sarah was in the middle of an explosive scandal as intimate snaps of her romping poolside with American businessman John Bryan were made public.
Any good relations between Philip and Sarah ended that day.
“He was furious because he saw it as her undermining what he had taken years to establish – undermining the monarchy, undermining her own husband,” Ingrid reveals.
Philip banned his former daughter-in-law from all royal occasions, and commentators in the UK’s Daily Express newspaper claimed they “can’t be in the same room together”.
And relations became even more strained in 2010 when Sarah was caught demanding £500,000 from an undercover newspaper reporter posing as a wealthy Arab businessman, in return for promising to arrange business meetings with and access to Andrew.
Not too surprisingly, Sarah was left off the invitation list a year later to the wedding of her nephew Prince William to Kate Middleton.
But by the time Prince Harry married Meghan Markle in 2018, Sarah had inched her way back into favour and was invited. Philip, however, studiously avoided her throughout the ceremony.
It was not until months later at her daughter Princess Eugenie’s wedding that Sarah and Philip finally came face to face, 26 years since they last spoke.
Sarah was reportedly a “bag of nerves” at the prospect of meeting him, but on the day, they were all smiles for the cameras.
In a surprising move, Sarah was invited to dine with the Queen and Philip at Windsor Castle later that year.
But then the biggest royal scandal in years hit in 2019, as details leaked about the close friendship between Andrew and the late paedophile Jeffrey Epstein, with allegations the prince had sexual relations with one of Epstein’s alleged victims when she was 17.
Andrew’s BBC interview was a disaster and only raised more questions.
Sarah soon found herself caught up in yet another scandal, blamed for talking the prince into the interview in the first place.
With planning underway for Philip’s 100th birthday celebrations in June, Philip has opted to limit Andrew’s involvement with the party to an absolute minimum.
And Nigel Cawthorne, author of Prince Andrew, Epstein and the Palace, says the move has been “one of the toughest decisions Prince Philip will have had to make in his life”.
Making sure Sarah’s name is not on the invitation list is likely to have been a far easier decision.
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