Lady Sarah and Prince Charles in 1977. Photo / News Corp Australia
In a story with eerie similarities to The Other Boleyn Girl, Prince Charles had his sights set on Diana Spencer's older sister long before his turbulent royal marriage.
Lady Sarah Spencer had a fling with the heir to the throne back in 1977, six years before Charles and Lady Diana announced their engagement to the world, and set in motion one of the most tumultuous and dysfunctional periods in modern royal history.
Sarah — who, like Diana, inherited the title "Lady" in 1975 when her grandfather died — was only 22 when she began casually dating 28-year-old Charles.
At that time, the "playboy" Prince of Wales was in the midst of a decade-long dating spree and was under increasing pressure from the Palace to find a wife.
Charles had amassed a lengthy black book of exes, including Lady Angela Keating, the daughter of Prince Philip's private secretary, Fiona Cottrell, who posed for men's magazine Penthouse, and Sabrina Guinness, the granddaughter of Sir Arthur Guinness, who'd already had relationships with Mick Jagger, Rod Stewart, David Bowie and Jack Nicholson.
Then along came Lady Sarah Spencer — who had all the right connections to make her a suitable royal wife.
The Spencers had had close ties with the royal family dating back several generations, and Sarah's grandmothers had served as ladies-in-waiting to Queen Elizabeth, the Queen Mother.
They made an impressive society couple, and Sarah even accompanied Charles to the plush Swiss ski resort Klosters.
But it was during that lavish holiday that the whole union apparently came undone — in an explosive fashion.
Sarah reportedly met up with two reporters to "spill gossip" over dinner, and her words would eventually come back to bite her.
According to Nigel Nelson and James Whittaker, Sarah's head seemed to be "turned by the publicity" her royal connection had generated — and she even admitted to them that she'd started keeping a scrapbook of all the press clippings about her and Charles, which she intended to "show" future grandchildren.
But perhaps the most damning statement of all was Sarah's view on marriage to the future monarch.
"Sarah was disarmingly frank about her boyfriend and declared she would not marry Charles 'if he were the dustman or the King of England'," Whittaker said, adding that they'd also discussed her other relationships, previous alcoholism, and battle with anorexia.
"That was good news from where I was sitting and Sarah seemed delighted I was so keen to share it with the nation."
But according to Whittaker, when Charles saw the article, he was furious.
He reportedly told Sarah that she had just done something "incredibly stupid" and promptly called off the romance.
Despite their abrupt split, it seems the pair harboured no hard feelings in the long term.
Just months later, Charles met Sarah's 16-year-old sister, Diana. Not only did Sarah give them her blessing, she also later claimed that she'd actually set them up in the first place.
"I introduced them; I'm cupid," she told
The Guardian.
Fast forward four years to 1981, and Diana, 20, was standing at the altar, exchanging marriage vows with Charles, 32, in front of 750 million people worldwide.
Diana became the Princess of Wales — a title which at one point, looked likely to have been her sister's.
By then, Sarah had gone on to marry Neil Edmund McCorquodale. The pair have three children.
Sixteen years later, Charles and Sarah were again brought close together, this time in the most tragic of circumstances — to retrieve Diana's body from Paris and bring it home for the funeral.
Since that devastating event in 1997, Sarah has stayed close with her nephews, Prince William and Prince Harry.