A royal biographer has a theory about the once star-crossed lovers, and it’s not what you might think

It was one of the last century’s most iconic “remember-where-you-were-when” moments: On July 29, 1981, then Prince Charles wed Lady Diana Spencer in a fairytale wedding watched by 750 million people. It was, as Diana later said, the worst day of her life.

“I can’t marry him,” she told her sisters during a pre-wedding lunch. But she did. Of course, we all know the ending to that story. The unhappy, scandal-wrought marriage ended in divorce in 1996, but not before Charles’s enduring love for Camilla Parker Bowles had become common knowledge.

In 2005, Prince Charles finally wed Camilla, and by all accounts, they’re as happy together as Diana, who died in that tragic car crash in 1997, always suspected they’d be. Today, after Queen Elizabeth’s death and King Charles III newly ascended to the throne with the Queen Consort by his side, it’s clear their love has endured since they first began dating in 1972. So why didn’t Charles marry Camilla in the first place?

Why Couldn’t Charles just marry Camilla in the first place?

The question was tackled in Sally Bedell Smith’s biography, Prince Charles: The Passions and Paradoxes of an Improbable Life. According to Bedell Smith, right from the start Charles adored the then-Camilla Shand, who’s close in age to Charles (Diana was 13 years younger) and has always treated him as an equal rather than as someone she idolized. However, the royal family wasn’t interested in having Camilla as its princess. For one thing, she was perceived as an “experienced” woman, which was a nonstarter for the royal family back then in terms of a suitable spouse for Prince Charles. For another, she wasn’t perceived as “aristocratic” enough to be a princess, according to The Duchess: Camilla Parker Bowles and the Love Affair That Rocked the Crown by Penny Junor.

“Lovely for you two to have a fling, but this absolutely cannot end in marriage,” Prince Charles’s great uncle Lord Mountbatten advised him, according to the documentary The Real Camilla: HRH the Duchess of Cornwall. Soon after, Charles was called away on naval business overseas, and used the time to put distance between himself and Camilla. Camilla soothed herself by reconnecting with her former beau, Andrew Parker Bowles. And that’s precisely where Bedell Smith theorizes that a scheme was hatched to get Camilla married off to Andrew.

The forcing of Andrew’s “hand”

It’s rumored that Camilla’s father planted a fake Camilla-Andrew engagement notice in The Times, apparently forcing Andrew’s hand. Literally. Prince Charles returned home to news of Camilla and Andrew’s engagement. According to Bedell Smith, that fake engagement announcement explains why Charles didn’t marry Camilla. It led to Andrew’s actual proposal to Camilla; without it, Charles might have married Camilla, despite his family’s objections.

Instead, Camilla married Andrew Parker Bowles in 1973, and Charles went on to date a number of “suitable” women until he met Diana Spencer in 1980. But all the while, Camilla remained in his heart, and occasionally in his plans, as Charles himself admitted. By the end of 1995, the Parker Bowles couple was divorced, the Prince and Princess were on their way to divorce and Diana had famously told television interviewer Martin Bashir that “there were three of us in this marriage, so it was a bit crowded.”

The happy ending for the King and the Queen Consort

King Charles and Camilla Parker Bowles got their long-awaited happy ending in 2005, when they married in a civil ceremony, which his mother, Queen Elizabeth, did not attend (although she did turn up at the reception). At the time Camilla was given the title, “Her Royal Highness The Duchess of Cornwall,” and now that Charles is king, she is known as “Queen Consort.” They’re still happily married. Need help keeping track of everyone? Check out our royal family tree.