Key takeaways from BBC interview as Earl Spencer defends claims about King

Talking about his motivations for writing the book, Earl Spencer, aged 62, said it was his “duty… as an eyewitness to history” and as someone in the “final season of my life” with his parents dying in their sixties.

“I’m aware of mortality and I wanted to just put things down once and for all that were true,” the historian and journalist explained.

“This is not a threat, it’s a fact, I know lots of things about the King which I chose not to include in the book because they were not relevant.”

When put to him that the statement sounded like a threat when it involved potentially damaging information, he said: “No, not at all a threat, it’s just the reality.”

Kuenssberg questioned why he included an account of a conversation in which his sister told him Prince Charles was in love with his valet – a claim Earl Spencer said was improbable – and asked if he was motivated in including some of these allegations to create interest to sell the book.

“It’s in the context of a conversation where Diana is telling me that her marriage is over,” the earl replied.

“It’s a brother’s tribute, a loving tribute to a sister. And I think she deserves honesty so that’s what I’ve delivered.”

The earl said he considers Swan Song: Diana, My Sister to be his “sign off” and final take on the situation.

“I’m not here to bang on about Diana, this is my final word, celebration of her, and I will step off into the sunset now and not be available for comment.”