Princess Diana and Sarah Ferguson's friendship reportedly irritated Prince Charles.

The documentary "Diana & Sarah, The Royal Wives of Windsor" touched on the late Princess of Wales and Duchess of York's skiing holiday. In the footage taken during the trip, the two were smiling, laughing and even playfully shoving each other as they mess around with each others' skis. Princess Diana almost knocked her pal off balance.

Princess Diana and Ferguson seemed to be enjoying each other's company in the clip, but the documentary claims that the scene was "too much" for the Prince of Wales, especially since there were photographers in front of them. The future king observed a strict "limit to how royals should behave in front of the public," reported Anna Kretschmer, a journalist for Express.

Another clip showed Prince Charles standing off to one side with his brother Prince Andrew. The heir appeared disappointed with their behavior. But in another shot, Prince Charles reached out to Princess Diana to help her regain her balance.

At the time, Prince Charles' disapproving look was apparent. He grabbed Princess Diana's arm to help her stand upright on her skis. Prince Charles reportedly thought of the whole episode as "unbecoming" and blamed Ferguson as a "bad influence" to the People's Princess. Prince Charles apparently believes that "duty comes first," especially in public events and in front of the media.

Princess Diana and Ferguson were often seen together. They were photographed in an animated conversation several times in the course of their friendship. In one of their many shots, Ferguson couldn't seem to stop herself from grinning.

"Diana was one of the quickest wits I knew; nobody made me laugh like she did," Ferguson wrote in her 2011 book "Finding Sarah." "We took vacations together with our children. Sadly, at the end [of the Princess's life] we hadn't spoken for a year, although I never knew the reason, except that once Diana got something in her head it stuck there for a while."

Just recently, Ferguson confessed that she remembered Princess Diana during her daughter Princess Eugenie's royal wedding. According to her, she was sure that the princess would have loved it if she was alive.

"Diana was my best friend and the funniest person I knew. She had such timing and wit," Ferguson said. "It was a total joy to be with her because we just laughed and enjoyed life so much, and I know she would have loved the wedding."

Princess Diana and Sarah Ferguson
Prince Charles and Sarah Ferguson's friendship irritated Prince Charles who found the two ladies' behavior in public "too much" for a royal. Pictured: Queen Mother, Queen Elizabeth II, Prince Andrew, Ferguson, Lord Linley, Prince Edward, Prince Charles and Princess Diana pose outside Clarence House on Aug. 4, 1989. Getty Images/Johnny Eggitt