Unheard audio tapes of Diana, Princess of Wales, talking about the King and her ‘hatred’ for stepmother Raine Spencer is to air in an upcoming documentary.

The recordings of Diana were taped three decades ago for her biographer Andrew Morton, who went on to publish the book Diana: Her True Story in 1992.

On Friday, a few extracts of unheard clips were shared through ABC News ahead of the release of documentary Diana: The Rest Of Her Story.

It serves as a follow-up to 2017 film Diana: In Her Own Words, both directed by Tom Jennings.

Speaking about her relationship with Charles, Diana says: “He was so grown-up and here was Diana, a kindergarten teacher. I mean the whole thing was ridiculous.”

Diana later spoke about her husband’s relationship with her family, revealing “he won’t even talk to mummy”.

She continued: “Because at Harry’s christening, Charles went up to mummy and said ‘we were so disappointed, we thought it would be a girl’ and mummy snapped his head off and said ‘you should realise how lucky you are to have a child that’s normal’.

“And ever since that day, a shutter’s come down, and that’s what he does when he gets somebody answering back at him, so to speak.”

The release of the clips comes a day after the 26th anniversary of Diana’s death on August 31 1997, following a car crash in Paris, and a week before the first anniversary of the death of the late Queen.

The clips also hear Diana’s feelings towards her stepmother Raine, who married her father John in 1976 before his death in 1992.

Speaking of her strained relationship with her stepmother, Diana says: “I was so angry. And I said I hate you so much. If only you knew how much we all hated you for what you’ve done. You ruined the house.

“You spent daddy’s money. I have said everything I possibly could and Raine said you have no idea how much pain your mother put your father through.

“I said pain Raine? It’s one word you don’t even know how to relate to.

“In my job and in my role, I see people suffer like you’ve never seen. And you call that pain? I said you’ve got a lot to learn.

“I remember really going for her gullet.”

It comes two days after the Duke of Sussex’s Netflix docuseries Heart Of Invictus was released, where Prince Harry recalls the triggering return from his final tour of Afghanistan which related to the trauma of losing his mother Diana.