Charles Spencer had a heartfelt conversation with his late sister's friend on Wednesday, and he shared never-before-revealed details about his angry reaction to some family wedding news.
Speaking to Julia Samuel, a therapist who was a close friend of Princess Diana on the latest episode of her podcast, Therapy Works, Charles opened up about several emotional topics, including the abuse he experienced at boarding school.
He also talked about his relationship with his parents, revealing he was "furious" when he was told that his father was getting re-married.
John Spencer, the 8th Earl Spencer, was married to Charles' mother Frances from 1954 to 1969 and the couple had four children: Charles, Diana, and their older sisters, Sarah and Jane.
In 1976, he married Raine Spencer, née McCorquodale, news that Charles admitted he was unhappy about – especially because he heard the news from an unexpected source.
As the father-of-seven told Julia: "One of my major memories from the time at prep school was being summoned in the summer of 1976, I'd just turned 12, for the headmaster to tell me that my father was marrying my stepmother, and I was furious."
He went on: "I remember I said to the headmaster, who I was terrified of, 'I can't believe he hasn't got the courage to tell me himself,'" Charles confessed.
"My mother leaving home, she fell in love with someone, these things happen, but it was all done so badly."
Sharing more insight into his dad's state of mind, the Earl movingly continued: "I have no doubt my father loved us enormously, he was actually a very sweet man but... After my mother left, I think he limped along for the rest of his life as an undiagnosed depressive and it would have been against his culture, or his knowledge, actually, to have sought help."
Raine Spencer and the late Princess Diana were rumoured to have a strained relationship following her marriage to the children's father but they were believed to have reconciled before the Princess died in 1997.
"Diana was a lovely person," the Countess told The Gentlewoman magazine before her own death in 2016. "She had incredibly heavy pressures put upon her, but we ended up huge friends. She used to come and sit on my sofa and tell me her troubles. I'm very happy about that."
Raine was the only daughter of Alexander McCorquodale and the bestselling romance novelist Dame Barbara Cartland and shared four children with her first husband Gerald Legge, 9th Earl of Dartmouth.
It was during her marriage that she became highly interested in politics and at the age of 23, she became the youngest member of Westminster City Council as a conservative.
Raine met Earl Spencer, her colleague on an architectural heritage committee, in 1973. Three years later she was divorced from her first husband and went on to marry John in July 1976, when Diana was 15 years old.
Charles and Julia briefly mentioned the late Princess during their chat, with the therapist saying of her beloved friend, "We miss her."