Camilla Parker Bowles' invitation to Prince Charles and Princess Diana's royal wedding was necessary for a reason.

Prince Harry invited two of his exes when he married Meghan Markle last May. However, the Duke of Sussex was not the first royal to do so. The Prince of Wales also invited his ex-girlfriend, Camilla, when he tied the knot with Princess Diana.

According to Emma Costello, the Duchess of Cornwall's attendance made sense because her then-husband, Andrew Parker Bowles, had a significant role in the wedding procession. Andrew was the commanding officer of the Household Cavalry Mounted Regiment. He would oversee the ceremonial escort that accompanied the couple's carriage ride through London.

Aside from this, Prince Charles and Camilla had been friends for a decade, even after they split. Their romance was short-lived, but their connection continued. 

According to a royal biographer, the royals didn't approve Camilla for the future king. They perceived her as an "experienced" woman which is not a suitable spouse for the heir to the throne. In addition, Camilla was reportedly not "aristocratic" enough.

"Lovely for you two to have a fling, but this absolutely cannot end in marriage," Prince Charles' great-uncle, Lord Mountbatten, reportedly advised the Prince of Wales when he was still dating Camilla.

Camilla and Prince Charles romance didn't last long after he went abroad for an overseas duty. Camilla decided to marry Andrew. After a few years, Prince Charles decided to exchange "I do's" with Princess Diana. However, their respective marriages ended in divorce and they rekindled their romance.

Prince Charles admitted that he had an affair with Camilla while he was still married to Prince William and Prince Harry's mom. On the other hand, Princess Diana admitted earlier that their marriage wasn't easy because there were three of them and it was a bit crowded.

According to Princess Diana's royal butler, Paul Burrell, the People's Princess suspected Prince Charles of plotting an automobile accident to kill her. Princess Diana was convinced that Prince Charles wanted to marry Camilla.

"Her words were 'these next few months, are the most difficult months of my life. I fear my husband is going to kill me. In an automobile accident. With head injuries. In order that he can remarry,'" Burrell recalled. "That is spooky. She predicted her own death nine months before she died."

Prince Charles and Camilla Camilla Parker Bowles invitation to Prince Charles and Princess Diana made sense for these reasons. Pictured: Camilla and Prince Charles in the White Drawing Room at Windsor Castle after their wedding ceremony, April 9, 2005 in Windsor, England. Photo: Getty Images/Hugo Burnand