Why Prince Charles broke off his relationship with Princess Diana's older sister, Sarah Spencer.

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Years before Prince Charles began courting an 18-year-old named Lady Diana Spencer, he had a brief relationship with her older sister, Sarah.

The year was 1977 and Prince Charles, then in his late 20s, was seeing the 22-year-old daughter of the Earl of Spencer.

Not much is known about their brief romance, but it’s believed that Charles ended their relationship because Sarah spoke too openly with the media about it.

A UK journalist even believes that one conversation he had with Sarah, who has since married Neil Edmund McCorquodale, was the reason the Prince of Wales called things off.

In a 2013 Mirror article, reporter James Whittaker said that during a lunch Sarah told him she wouldn’t marry Charles “if he were the dustman or the King of England”.

He recalled printing the words at the time and shortly after learning that the couple had broken up.

Whether or not Sarah had told James that she wasn’t marrying Charles because she wanted to shut down rumours of their relationship or because she really didn’t want to marry him, it seems it may have ended their relationship.

According to biographer Andy McSmith Sarah was “frozen out of the royal entourage” after the 1977 article was printed.

However, Sarah didn't seem to hurt by the breakup, at least not years later when she claimed that she introduced Prince Charles to his future wife, her little sister Diana.

After the couple, who had began dating in 1980, announced their engagement in 1981, Sarah was quoted as saying: "I introduced them, I'm cupid."

By then Sarah had been happily married to her husband Neil Edmund McCorquodale for about a year. The couple has since had three children together, Emily, Celia and George.

Her sister, meanwhile, married Prince Charles in the wedding of the decade in July 1981.

But the future King's second relationship with a Spencer wasn't to end happily either, with the couple divorcing in 1996 after years of separation.