The documentary is based on recordings of meetings between Princess Diana and her voice coach, Peter Settelen, at Kensington Palace in 1992-93. The princess spoke candidly about her marriage, and her tense relationship with the royal family, including her description of how Queen Elizabeth II reacted when she asked the monarch for advice about her failing marriage with Prince Charles. The tapes include her discussing Charles's relationship with Camilla Parker Bowles, whom Charles later married in 2005. The documentary will show Diana talking about Charles's attempts to woo her during a barbeque in 1979 when she was 18 and her falling "deeply in love" with a man widely believed to be her bodyguard, Barry Mannakee.

Settelen says there were 12 recordings. He kept 7 but the tapes got lost. Following the Princess’s death in 1997, police held some of the videotapes after they were seized in ex-royal butler Paul Burrell's home in 2001. Diana's family tried to make a legal claim to the recordings, but they were returned to Settelen in 2004. Excerpts of the recordings were aired in the US in 2004 but they have never been screened in Britain.

Diana and Charles married in 1981 and divorced in 1996 after having two sons,  Prince William and Prince Harry. This year marks the 20th anniversary of Diana's death in a Paris car crash on August 31, 1997, which was followed by an outpouring of grief in Britain and beyond. A documentary entitled “Our Mother: her life and legacy” was screened in Britain on July 24.