The Duke of Cambridge and Prince Harry have given their “final word” on their mother in a new documentary, its director has said.

Diana, 7 Days details the week of the death of the Princess of Wales and the national outpouring of grief that followed.

A screengrab of The Duke of Cambridge from the BBC’s Diana, 7 Days (Sandpaper Films)

It includes interviews with her sons and siblings, as well as former members of the Royal Household and former Prime Minister Tony Blair.

Henry  Singer, the filmmaker who made the Twin Towers documentary The Falling Man for the fifth anniversary of 9/11, said he was allowed to ask William and Harry anything for the BBC’s new 90-minute programme, although they could choose not to answer.

He told the Radio Times: “They talk about coming down to London, what it was like to go outside, and how people were so anxious to see them, and how people were crying, and yet they didn’t cry.”

A screengrab of Tony Blair from Diana, 7 Days (Sandpaper Films)

Singer added that Harry, who was 12 at the time, talks about deliberately trying to suppress any tears while the huge crowds around him were weeping openly and that William speaks of viewing the procession behind her coffin through the “safety blanket” of a bowed head and his long fringe.

Singer said: “My film may not have the headlines that other films have had, but I would like to think I will do something that lasts the test of time, and that, for me, is much more important than breaking news.”

The latest cover of the Radio Times magazine

He continued: “I think the Princes hope they have answered these questions once and for all, and they don’t need to be asked them anymore, and that people can refer back to this film and our words within it if they have questions. That this is their first, and final word on it.”

The full interview is in Radio Times, which is on sale now.