A new Princess Diana documentary featuring five hours of explosive audio tapes made before her death could shed light on some of the sensational claims made recently by her brother, Earl Spencer.

‘Diana Unheard’ is based on secret recordings made by the late princess which she passed on to author Andrew Morton via her friend, Dr James Colthurst.

They were used as the basis for his book, Diana: Her True Story which was published in 1992, although Diana’s involvement was not revealed until after her death in 1997.

Now its producers have claimed the tapes ‘cover some of the ground explored by her brother, Earl Spencer, in his recent book Swan Song’ which sparked a war of words between himself and Buckingham Palace.

In an interview with Deadline they say Diana openly talks about her marriage, her sons and the line of succession, and even about the former Prince Andrew, who was stripped of his titles last year over the association with convicted paedophile Jeffrey Epstein.

She also speaks about her relationship with Queen Camilla, then Camilla Parker Bowles, and recalls a story about an alleged confrontation between the two women over the then Prince of Wales.

Speaking to the publication about the project for the first time, Kerene Barefield, Creative Director of Love Monday TV, which is producing Diana Unheard, says their aim is to ‘reframe the narrative around the Princess and give her a voice, almost three decades after her tragic death’.

‘The media always gave us this tragedy that Diana was sad and lonely and she was manipulated,’ she says.

The Prince and Princess of Wales during a trip to Toronto, Canada 

‘These tapes don’t tell that story at all. They tell a story of an incredibly brave woman who had agency and knew what she wanted and how she was going to get to it.’

However the three-part series, due to come out next year around the 30th anniversary of Diana’s death, is set to be uncomfortable for Buckingham Palace, which has already had to face down a series of vitriolic claims by her brother, Earl Spencer, in recent weeks.

They have dismissed his claims that the King seemed ‘giddily elated…like a lottery winner’ at his ex-wife’s death and that he ranted during a tense phone call ‘we’ll forget her soon enough’, as being clouded by grief.

Intriguingly, production company Love Monday has previously made programmes in conjunction with Buckingham Palace, including a documentary about Queen Camilla’s work combating domestic violence.

The series is apparently due for a ‘big launch’ at an industry event next week with details of who will air it worldwide due to be revealed soon.

Barefield says the idea came up after author Morton appeared on another one of their shows and she asked him where the tapes were.

Morton, publisher Michael O’Mara and Colthurst himself decided to give permission for the tapes to be used and will all appear in the three-part programme. Her former lover James Hewitt has also been interviewed for it.

While some excerpts from the tapes have been aired over the years, no-one has been given access to all of them until now.

Deadline reports that the documentary’s three parts are entitled: Got To Get Out; You’re On Your Own; and Time Is Precious.

Barefield says: ‘Something I don’t think people understand at all, is that how she [Diana] took agency to get this book out, and her reasons for wanting it out. But also how, when it came out, no one could know that she had anything to do with it.

‘One of the things I loved when I first heard the tapes was just hearing her laughter. In the middle episode, we go back to her childhood. There’s all this stuff that you wouldn’t expect and I think it shows that she had that agency and that kind of drive from a very young age.

Earl Spencer’s recent book Swan Song’ sparked a war of words between himself and Buckingham Palace

‘And then the final episode brings it all back to the book again, and you start getting this countdown to when it is going to come out, and there is this time bomb that’s ready to explode.’

She adds: ‘This is what Diana would have done if she was still alive today. That’s how we framed it. It’s her documentary.’

But both the producers, Morton and Colthurst will undoubtedly face criticism for ‘cashing in’ on the late princess, particularly as her son, Prince William, has repeatedly asked for her memory to be left in peace.

He is known to be concerned that much of his mother’s collaboration with the media – including the by now infamous Panorama interview he believes should never be aired again – came at a particularly vulnerable time in her life.

It is likely that many critics will say Diana clearly never intended for the audio tapes to be made public and that she may well have felt differently now.

Indeed, there is much evidence to suggest that she and the then Prince Charles had a much better relationship at the time of her death and Diana wished him well.

It has also been confirmed that Prince Harry is exploring ways to mark the 30th anniversary of his mother’s death including a possible documentary.