Prince Charles hid his affair with Camilla Parker Bowles from Princess Diana with the help of the royal staff.

According to Andrew Morton in his book “Diana: Her True Story,” the Princess of Wales had strong suspicions about Prince Charles and Camilla having an affair when they were still engaged. However, those close to the future king denied the affair and some even questioned Princess Diana’s sanity, Reader’s Digest reported.

Queen Mother reportedly told her friends that Princess Diana was a “silly girl“ for imagining things. Also, Prince Charles’ staff helped him hide his illicit affair by covering him up.

Prince Charles’ bodyguard was forced to accompany him on his nighttime visits to see Camilla. His chef and butler were instructed to cook dinner even though they knew that he would be out with his lover.

Also, Prince Charles’ valet was instructed to mark up the TV listings guide to make it look like he spent the night at home watching television. When Prince William and Prince Harry’s dad broke his arm in a polo accident, his staff listened to police radios to track Princess Diana’s trip so they could get the Duchess of Cornwall out of Prince Charles’ room before Princess Diana arrived.

Princess Diana revealed in her infamous interview how she told Prince William about Prince Charles and Camilla’s affair. The People’s Princess said in the interview that “there were three of us in this marriage” before adding that the “pressure of the media” took a toll on their relationship. Princess Diana made her eldest son understand that those two issues were “very difficult” to handle.

Princess Diana made Prince William understand that she still loved Prince Charles but they could no longer live together. Princess Diana told Prince William everything without blame and anger so it would be easier for him to accept it.

In related news, Morton revealed that Princess Diana was “absolutely miserable” and sounded “like a prisoner of the Palace” when she was still with Prince Charles. He confessed that Princess Diana chose to work with him because he was “independent and sympathetic to her cause.”

Prince Charles and Princess Diana
Princess Diana and Prince Charles attend a welcome ceremony in Toronto at the beginning of their Canadian tour on Oct. 1, 1991. Getty Images/Jayne Fincher