Channel 4 defends its use of intimate recordings in Diana: In Her Own Words

Amid an array of speaking exercises, the recordings show frequent moments when the princess talks candidly about her private life, the infidelity of her husband and her close relationship with her royal protection officer Barry Mannakee.

Channel 4 insist that the tapes are a valid public document which show the spontaneity and charm of the princess in unguarded moments. They believe that the 20th anniversary of her death on 31st August 1997 is an important landmark and sources point to the candid interviews given by Diana’s sons, Princes William and Harry, to ITV.

The broadcaster has notified the royal family and not received a response. And it has declined to speculate on the likely impact showing the tapes will have on Diana’s family, including her sons.

When asked by RadioTimes.com whether viewers may feel uncomfortable watching exchanges which Diana may have had a reasonable expectation to presume would have been kept private, Ralph Lee, C4's deputy chief creative officer, said: “I don’t think people will look at that and say those are private exchanges. I think they will look at it and say that’s a public figure sitting down and being interviewed which is a familiar process, we see that on the news we see it in documentaries all the time.

"She is very clearly talking to someone in front of a camera, there’s nothing surreptitious. The word that has been used is that the footage is somehow ghoulish …but no-one could see this and say the content is ghoulish. I simply don’t agree with that. She’s self-consciously clearly taking part in a filmed process.”.

“It’s a big anniversary and 80 years on from the abdication crisis we are still making documentaries about Edward VIII and Wallis Simpson. At the end of the day, if you have a monarchy, the personal, the familial, the aspects of their lives ... are really important to the nation’s history.

"With this big anniversary, we wanted to feel we were going after something different from other channels. We knew there were going to be multiple perspectives on Diana and on her life...and access to the Settelen tapes meant that we could be front and centre of the story and allow her to tell the story as much as possible in her own words.

"The fact that it dwells so much on her difficulties is a product of what she thought was important. Those are things she chose to use in giving herself a connection with the British public."

Lee said that Channel 4's show was "in the same spirit" as ITV's recent documentary Diana Our Mother: Her Life and Legacy which heavily featured contributions from William and Harry.

He added: “In many ways it was in the spirit of what you see in this documentary and the way Diana worked. She was an important public figure, a member of the Royal Family who admitted to having vulnerabilities and having emotions and that was very rare and gave her a very strong connection with the British public and it brought a lot of power and a lot of force to the work she did with vulnerable people.”

Ken Wharfe, Diana’s former royal protection officer who appears in the film (below), said at a screening: “I think this is a film that both William and Harry should see because I think they will see a side of their mother that they themselves have endorsed and it is... important."

Diana's former private secretary, Patrick Jephson, added: "What Peter Settelen was trying to do was make Diana speak with her own voice, an authentic voice, because that’s what people hear."

Asked if Settelen was being "devious" in prompting personal revelations from Diana in the recordings, he added: “There may be an element of that but she recognised that if she’s going to speak in public on the sorts of issues she championed then it has to sound authentic, it has to sound real.

“He was saying: 'Diana ... tell me your stories. If you are going to lead from the heart you need to speak from the heart too'.”

Diana: In her Own Words will air on Channel 4 on Sunday August 6