EXCLUSIVE: Secret Princess Diana Tapes Set to 'Pile Even More Pain' on King Charles

King Charles faces another painful revisiting of his marriage to Princess Diana after hours of her intimate recordings were secured for a documentary that will examine her private thoughts about the monarch and the Royal Family.

RadarOnline.com can reveal how the 77-year-old King's relationship with Diana, who was 36 when she died in Paris in 1997, will return to the spotlight in Diana Unheard, a three-part series produced by Love Monday TV and distributed internationally by Cineflix Rights.

Producers have obtained hours of conversations secretly recorded in 1991 between Diana and her friend James Colthurst – material subsequently used by Andrew Morton for his book Diana: Her True Story.

A royal source claimed: "For Charles, these secret Diana tapes threaten to reopen an intensely difficult chapter just as the controversy surrounding Earl Spencer's book has brought Diana and the breakdown of their marriage back into headlines. They will pile even more pain on Charles.

"Whatever Diana says about Charles in these recordings will be picked apart word by word.

"These tapes come from an extraordinarily unhappy period in the marriage. They are Diana's perspective at that moment, rather than a complete account of everything that happened, but that distinction can easily become lost when material this intimate is broadcast around the world."

The insider continued, "There is a sense that Charles cannot escape being pulled back into events from more than three decades ago. First there are allegations from Diana's brother, and now there will be hours of Diana discussing her life and relationships in her own voice."

Richard Life, senior vice president of acquisitions and co-productions for Cineflix Rights, said: "What really sets Diana Unheard apart is the unique opportunity to hear several hours of intimate recordings of the Princess – her own story in her own voice at a pivotal point in her life."

The conversations are said to cover Diana's life, love and experiences within the Royal Family, including discussions about the then Prince Charles, Camilla, and Prince Andrew.

Colthurst and Morton worked with Love Monday TV to provide access to the recordings, and both appear in the series.

Kerene Barefield, creative director at Love Monday TV, said: "In making Diana Unheard, we wanted to challenge the narrative that has too often portrayed Diana, Princess of Wales, simply as a victim of her circumstances.

"This is Diana not as a passive victim of events, but as a woman taking control of her own narrative and risking everything to make her voice heard."

"Diana Unheard restores authorship of one of the most scrutinised lives in modern history to the woman at its centre," Barefield added.

The documentary arrives amid a separate confrontation between Buckingham Palace and Diana's brother Charles Spencer, 62, over allegations contained in his memoir Swan Song: Diana, My Sister.

Spencer claims Charles told him after Diana's death: "Rest assured, we'll forget her soon enough!"

Buckingham Palace issued an unusually direct response challenging Spencer's recollection.