Charles Spencer revealed one of Princess Diana's biggest fears during a brave interview on Monday.
The ninth Earl Spencer, 59, sat down with the Times ahead of the release of his new book, A Very Private School, in which he discusses the abuse he said he suffered whilst at Maidwell Hall Prep School.
During the harrowing conversation, Charles also opened up about how his late sister cared for him after their mother left the family home. He explained one of her great fears was the dark.
Charles said: "Diana looked after me because she was nearly three years older than me. She said that the worst part was hearing me cry down the hall because she was terrified of the dark and couldn’t come to me."
The Earl had a very close bond with his sister and also explained how he felt it was his duty to keep Diana grounded following her relationship with Prince Charles.
He said: "I remember going to a dinner soon after she'd become what she became, given by sort of friends in a private room in a restaurant in Fulham. I remember thinking, 'Crikey, they're all sucking up to her like crazy.' I realised that my job was to be absolutely solid as a brother and just remain the same.
"That was sometimes difficult, because I'd say things that people weren't saying to her in a loving way, a constructive way, and I think it was tricky for her to hear anything except how marvellous life was — but I thought that was my duty. I was her little brother. We grew up together."
Charles and his wife, Lady Karen Spencer live at Althorp House where Princess Diana is buried.
The couple often shares wonderful updates from the grounds of the property, where they have a growing list of animals, including two pet sheep, Lucky and Minty as well as a visiting peacock, Tim.
The candid interview came just one day after the news was announced that Charles had become a grandfather for the first time. His daughter, Lady Kitty Spencer, welcomed her first child with her husband, South African-British businessman Michael Lewis.
Kitty, 33, shared the news with a surprise photo on Mother's Day with an adorable photo of herself holding her newborn.
"It's the joy of my life to be your mummy, little one. I love you unconditionally. Happy Mother's Day to those who celebrate today."