Diana confessed to her voice coach Peter Settelen she once pushed Raine down the stairs at the family’s ancestral home, Althorp.

She and brother Earl Spencer kicked their stepmum out of the property the day after their father’s death — despite his wish for her to remain for at least six months.

A former pal of Raine tells the show how the hatred was mutual, with the Countess accusing Diana of “never reading a book in her life”, and sniping:

“She has nothing to talk about beyond Duran Duran.”

Yet Diana later grew close to Raine and fell out with her own mum Frances Shand Kydd.