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A new documentary on Diana which promises to be the "definitive account" of her life is planned for ITV later this year, as the princess would have turned 60.
Diana was killed in a car crash in Paris in 1997, at the age of 36.
In what would have been a landmark birthday year for the princess, ITV has confirmed a one-off special documentary as well as a three-part series to remember her.
The one-off film, to be called Diana, will use never-heard-before testimony and rarely seen archive footage as well as letters and photographs from those close to her.
It will trace her journey from nursery worker to member of the Royal Family.
Production company 72 Films will be behind the programme, and it will be directed by Bafta winner Jemma Chisnall.
David Glover, executive producer for 72 Films, said: "There is something a bit magical about Princess Diana, and despite the difficulties in her personal life she managed to use her connection with people to do huge amounts of good.
"Her 60th birthday feels like the perfect time to re-examine her life and legacy and explore just how she went from a relatively unknown teenager to (such a ) much-mourned person."
Jo Clinton-Davis, controller of factual entertainment for ITV, added: "This year would have been Diana’s 60th birthday, and the intention with this landmark documentary is to offer the definitive account of her life, both in front of the cameras and behind the scenes.
"It is a difficult undertaking to shed new light on the most emotional, dramatic and pivotal elements of the life of Diana, when that light still burns brightly.
"But by delving deep into her relationships with friends, colleagues and staff, our aim is to provide a vivid portrayal of the woman who became known as the Queen of Hearts."
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ITV is also planning to show a three-part series called Diana’s Decades, which will follow her early royal life, her work with HIV charities and her friendships with Hollywood celebrities.
It will also look at how she became the 'People's Princess', and explore the changing face of Britain at the time of New Labour's success in 1997.
Daniela Neumann, of production company Spun Gold TV, said: "Nearly 25 years on from her tragic death, Diana, Princess of Wales continues to lead our news bulletins and conversations not just in Britain but around the world.
"Diana’s Decades takes a fresh approach to recounting her life and legacy by looking at how she was shaped by the changing world around her and as a result transformed not just the monarchy but also society more widely as her legacy."
The new programmes come after Harry, William, and Diana's brother Charles, the Earl Spencer, laid heavy criticism at the BBC's door over an interview the princess did with Martin Bashir in 1995.
A report into the way Bashir convinced Diana to sit down with him found he was "devious and dishonest" in his approach. William said the BBC had "failed" his mother, while Harry said the practices which allowed that "ultimately took her life".
Earlier this year an appeal for home footage of Diana was made by Lightbox, the company behind Whitney, about the late Whitney Houston, as they also prepare to make a film about the princess for cinemas.
Lightbox is making a theatrical documentary which it says will unfold 'in real time'.
Diana's sons, Prince William and Prince Harry, have also planned their own tribute to their mother in the year she would have been 60.
They will be unveiling a statue of her in the sunken garden at Kensington Palace on 1 July, standing shoulder to shoulder for the first time in public in many months.
Though they were spotted chatting after the funeral of Prince Philip, they were separated from walking next to each other ahead of the coffin by their cousin Peter Phillips.
Harry and William have both paid tribute to their mother by giving their daughters Diana as a middle name.
William, 38, welcomed Charlotte Elizabeth Diana back in 2015, and Harry, 36, welcomed Lilibet Diana on 4 June.