Prince William says filming documentary about his mother Princess Diana 'a healing process'

Prince William said speaking openly about his mum for a new documentary about her life was "daunting" at first but the process has been a "healing" one.

William described the 90-minute programme as a "tribute" to Diana that will remind the public - especially those too young to remember her - of the "warmth" and "humour" of the global figure.

But the ITV film will be the first and last time he, and Prince Harry, will speak candidly about their mother.

Speaking ahead of the programme's screening on Monday, William said: "We won't be doing this again - we won't speak as openly or publicly about her again, because we feel hopefully this film will provide the other side from close family friends you might not have heard before, from those who knew her best and from those who want to protect her memory, and want to remind people of the person that she was.

"The warmth, the humour and what she was like as a mother, which probably hasn't come across before in many other pieces and from other people."

William is interviewed extensively with Harry for the ITV programme Diana, Our Mother: Her Life and Legacy, which also features the Princess' brother Earl Spencer and friends like Sir Elton John.

During the film, screened on Monday, an intimate portrait of the woman is built up with her son's poignant and funny recollections at its core, as they reminisce with the help of never-before-seen family pictures of them taken by Diana.

Explaining his reasons for speaking candidly about Diana, William said: "Twenty years on Harry and I felt that it was an appropriate time to open up a bit more about our mother."

The 20th anniversary of her death will be marked with a statue of Diana erected in a place she knew well, the public gardens of her former home Kensington Palace.

William said: "Harry and I feel very strongly that we want to celebrate her life and this is a tribute from her sons to her, and we want her legacy to live on in our work and we feel this is an appropriate way of doing that.

"To remind not only people who knew her, but also you have to remember this is 20 years ago now she died and there are people who don't even know about her.

"Twenty-five year olds who probably have just heard the odd snippet about her, and know a little bit about who she was but nothing really about her, so this is introducing her to a new audience as well.

"And I think it's been quite cathartic for us doing it. It's been at first quite daunting - opening up so much to camera...but going through this process has been quite a healing process as well."

• The documentary, Diana, Our Mother: Her Life and Legacy will be screened on ITV on Monday