Princess Diana had a shocking reaction to Prince Charles’ proposal several years ago. And the reason behind it has finally been revealed.

In the Channel 5 documentary “Charles And Di: The Truth Behind Their Wedding,” royal expert Ingrid Seward revealed that the future king invited the Princess of Wales to Windsor Castle one day. After she arrived, Prince Charles told his then girlfriend how much he missed her.

Prince Charles then asked for Princess Diana’s hand in marriage, and the mom of two started laughing. Seward said that the laughter was probably triggered by the late royal’s nerves. “She didn’t think it was the most romantic of proposals but she had the proposal,” Seward said.

Royal biographer Christopher Wilson added that Princess Diana was surprised when Prince Charles asked for her hand in marriage. After all, the royal couple’s relationship was far from being happy and perfect.

And during one of her interviews, Prince William’s mom shared details about the proposal. She shared the first thing that Prince Charles told her before he asked to marry her. The heir to the throne reminded Princess Diana that she will become Queen one day before telling her how much he loved her.

“He said, ‘whatever love means,’” Princess Diana revealed. “He said it then. So I thought, that was great. I thought he meant it,” she added.

Prince Charles and Princess Diana The Prince and Princess of Wales leave Gibraltar on the Royal Yacht Britannia for their honeymoon cruise, 31st July 1981. Jayne Fincher/Princess Diana Archive/Getty Images

It didn’t take long for Princess Diana to say yes to Prince Charles’ proposal. But in a shocking twist, it seems that the dad of two wasn’t really keen on proposing to Princess Diana.

After asking the mom of his sons to marry him, Prince Charles called Queen Elizabeth II on the phone to tell her that Princess Diana said yes. “He rang his mom, simply to say there, ‘I’ve done it now. You’ve asked me to get married to somebody and I’ve fixed it,’” Wilson narrated. “What he’d done was he’d finally found a wife.”

However, the person whom Prince Charles really wanted to marry was Camilla Parker Bowles. Unfortunately, the Duchess of York wasn’t regarded as a suitable partner for the future king because she was already married to Andrew Parker Bowles.

Prince Charles and Camilla Prince Charles, Prince of Wales, and Camilla, Duchess of Cornwall, attend the opening of a new terminal at the Owen Roberts International Airport on March 27, 2019, in George Town, Cayman Islands. Phil Noble - Pool/Getty Images