The Duke of Cambridge and Prince Harry speak in detail about their mother's death, from the moment they heard the news, in a new BBC documentary.
Diana (a working title) will tell "the inside story of the tumultuous and unprecedented week that followed the death of Diana, Princess of Wales".
It will explore the impact she had on the nation and people around the world.
The film features in-depth interviews with her sons, speaking in detail about that week's events from the moment they heard the news of their mother's death to the day of the funeral.
They will also reflect on Diana's life and what she meant to them, both then and now.
The film will also include interviews with close friends, political figures and journalists, many of them speaking for the first time about the events of that week in August 1997.
The 90-minute BBC1 documentary comes after the broadcaster aired controversial royal drama King Charles III, adapted from a stage play, in which the Prince of Wales succeeds his mother but sparks a constitutional crisis.
And it has been revealed days after the BBC announced a new drama, in which the impact of Diana's death on the lives of ordinary people is explored.
The documentary was announced as part of 35 hours of new commissions across history, science, religion, documentaries and factual entertainment on the BBC.
Alison Kirkham, controller of factual commissioning, said: "We are living in a period of seismic change when it feels harder than ever to get to grips with what is happening around us.
"In an era of false facts and fake news, it is the role of a proudly independent BBC to respond by offering a trusted lens through which to view and understand the world."
She said: "Just a few years ago, many within the industry were predicting the demise of factual (programmes) in a multi-channel, multi-choice world.
"In fact the opposite has proven to be true."
She added: "No subject should be taboo. We can't and won't shy away from ambitious, complicated programmes."