Prince Charles was reportedly angered as he watched Channel 4's Princess Diana documentary.

Prince Charles

Prince Charles

The 68-year-old royal - who was married to Diana from 1981 until 1996 - is said to have watched the much-discussed 'Diana: In Her Own Words, in which she spoke candidly about her sex life with the Prince, and Charles was left feeling frustrated by what he saw.

A source said: "The Prince did watch it while doing other things.

"He was fuming because it brought all of this back up."

The Queen is also said to feel frustrated that the issue of Prince Charles' relationship with Diana has been thrust back into the spotlight.

The insider told the Daily Star newspaper: "Her Majesty also watched some of it.

"She is wanting to move on and she knows Diana was not looked after by the palace properly but she had always said we must learn from the past on how to move on.

"She certainly doesn't want all this brought back up again but she knows the interview was always out there."

Despite the criticism surrounding the documentary, it attracted an audience of 3.5 million viewers, making it the most-watched documentary on Channel 4 in three years.

A spokesperson for the broadcaster said: "The documentary attracted an average audience of 3.5 million viewers and a 16.4 percent share of audience, making it Channel 4's highest rating overnight audience since 'Gogglebox' in April last year and biggest overnight for a doc since 'Benefits Street' in Feb 2014."

Meanwhile, a Royal spokesperson has denied the claims of the insider, saying: "The story is entirely false."