Princess Diana was advised to wear a Camilla-style wig to spice up her marriage to Charles.

The allegations were made in a new book by royal biographer and The Crown historian Robert Lacey, who is looking into the couple’s bond.

The royal historian says the Princess of Wales would joke about attempting to get Charles intoxicated in order to encourage “a bit of princely ‘leg-over.'” The wedding of Prince Charles and Diana in 1981 was dubbed the “wedding of the century.”

Robert’s book says: “Diana would both bemoan and joke about the bedroom boycott with her girlfriends. Perhaps she should try to get Charles drunk one evening, she suggested, in the hope of encouraging a bit of princely ‘leg-over’

“‘Oh no’, they would respond, ‘You know what happens to the vital organ under the influence of too much alcohol – brewer’s droop’. ‘How about turning down the lights and wearing a blonde wig?’ asked one of them. ‘That way he might mistake you for Camilla.’

“Diana roared with laughter. After time and some rueful reflection, she had come to accept the reality of her husband’s ‘lady’ in his life.”

After Charles and Diana were married in 1981 in St Paul’s Cathedral and had two kids, William and Harry, their physical relationship quickly deteriorated.

Charles and Diana divorced in 1996 after a very public spat that saw the Princes appear on Panorama.

“Well, there were three of us in this marriage, so it was a bit crowded,” Diana famously remarked in a 1995 interview with the BBC.

Her bombshell discussion was viewed by 22.8 million people, making it one of the most popular BBC programs of all time.

Camilla, who was also divorced at the time, later married Charles in 2005.

Diana had already spoken up about her sex life during her meetings with speech coach Peter Settelen.

She said: “Well, there was [sex]. There was. There was. But it was odd, very odd.

“But it was there then it fizzled out about seven years ago, six years ago, well seven, because Harry was eight.”

Christine-Marie Liwag Dixon, the narrator of The List, said Diana was once left “in tears” following a dispute with Charles, prompting the strange wig story.

“Like most young royals, Prince William was sent off to boarding school at a young age,” Ms Liwag Dixon informed listeners.

“The experience was reportedly a difficult one for him at the beginning.

“As noted in the book ‘Prince William: A Biography’, the future king was sent to Ludgrove School when he was just eight years old.

“While his mother, Princess Diana, was reluctant to send him away, his father, Prince Charles, wanted to continue the family tradition of sending children to boarding school.”

“William was reportedly quite lonely after first going away to school and missed his family.

“Diana is said to have been in tears when she dropped him off at school.

“While he was said to be homesick as he adjusted to his new life at school, William eventually grew accustomed to being away from home, although it’d seem he still missed his family.

“His mother regularly wrote to him, reportedly addressing her letters to My Darling Wombat’.”