Princess Diana got a secret message from Prince Charles the eve before their wedding

A royal author revealed Prince Charles' secret message to Princess Diana on the eve of their wedding.

In her new book about Camilla, Duchess of Cornwall, Penny Junor shared the content of the note Charles sent to Diana the night before their royal wedding, as reported by Mirror.

"The night before the wedding, which Diana spent at Clarence House with her sister Jane, he sent her a note, along with a signet ring that bore the Prince of Wales feathers," Junor wrote.

Before Charles met Diana, he was in love with Camilla. But Camilla wasn’t viewed as virginal enough for a proper courtship and role as a royal wife.

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Express detailed, "He wrote: "I'm so proud of you and when you come up I'll be there at the altar for you tomorrow. Just look 'em in the eye and knock 'em dead.'"

Charles believed the wedding wasn't right, however, realized it was too late to pull out, the author claimed.

She also asserted that the late People's Princess changed in the lead up to their marriage and she ended up unhappy and mournful.

"Charles was not convinced he was doing the right thing in marrying Diana but there was no way out and, bolstered by the hope that things would be different once they were married, he put a brave face on it," Junor wrote.

Before Charles met Diana, he was in love with Camilla. But Camilla wasn’t viewed as virginal enough for a proper courtship and role as a royal wife, according to the USA today.

In 1973, Camilla was married to Andrew Parker Bowles. Charles, who also dated Diana's older sister, Sarah in 1977, was married to Diana in 1981.

Charles and Diana's relationship seemed stable at first. But in 1986, after the birth of Prince William and Prince Harry, Charles rekindled his affair with Camilla. Diana also began dating James Hewitt, her riding instructor.

Charles and Diana separated in 1992. Their divorce was finalized in 1996.

In 2005, Charles tied the knot with Camilla in a civil ceremony at Windsor Castle. Queen Elizabeth II and Prince Philip did not attend the marriage ceremony. But they attended the service of blessing at Windsor Castle's St. George's Chapel.

Camilla, who was automatically acquired rank as the second highest woman in the United Kingdom Order of Precedence, was known as the "most hated woman in Britain."