Prince William was just 15 and his brother Prince Harry only 12, when their mother, Princess Diana, was killed in a car crash in Paris on 31 August 1997. She was just 36 years old.
Twenty years later, the royal siblings have opened up about their mother's untimely passing in a new BBC documentary to mark the 20th anniversary of her death.
A 30-second trailer for the upcoming feature, sees the princes speak candidly about the way in which they coped with their mother’s death - in particular, the moment they were forced to walk behind her coffin in a funeral procession through the streets.
William recalled: "It was one of the hardest things I've ever done, that walk. I felt like she was almost walking along beside us, to get us through it."
Heartbreakingly, Harry remembered being comforted by strangers.
"I remember people's hands were wet because of the tears that they had just wiped away,” he said.
Prince William, now 35, recently explained that he and his younger brother felt compelled to speak on camera as a way to “stand up” and protect their mother - something they weren’t able to do at the time of her tragic passing.
"Part of the reason why Harry and I want to do this is because we feel we owe it to her," he said in a statement. "I think an element of it is feeling like we let her down when we were younger. We couldn't protect her. We feel we at least owe her 20 years on to stand up for her name and remind everybody of the character and person that she was. Do our duties as sons in protecting her."
Prince Harry, 32, added: "When she died there was such an outpouring of emotion and love which was quite, which was quite shocking. It was beautiful at the same time, and it was amazing, now looking back at it, it was amazing that our mother had such a huge effect on so many people.
"When you're that young and something like that happens to you I think it's lodged in here, there, wherever – in your heart, in your head and it stays there for a very very long time. I think it's never going to be easy for the two of us to talk about our mother, but 20 years on seems like a good time to remind people of the difference that she made not just to the Royal Family but also to the world."
Diana, 7 Days, will also feature a selection of interviews with those who were at the 'eye of the storm' in the days following the princess' death - including, among others, Diana's brother Earl Spencer, her sister Lady Sarah McCorquodale and the Princess' lady-in-waiting Anne Beckwith-Smith.
The two-hour documentary, directed by award-winning filmmaker Henry Singer, will reflect on the tumultuous week that followed the death of the People’s Princess - questioning what was it about Diana that propelled such an outpouring of grief?