Premise: Marjorie Minna Jenkins Pratt, Countess of Brecknock DBE, JP (died 24 August 1989), was a British peeress. She was the daughter of Colonel Atherton Edward Jenkins and his wife, Anna Isabella (née Schoenbrunn), the niece of Sir Ernest Cassel. She was a cousin (and life-long close friend) of Edwina Ashley, who married Lord Louis Mountbatten, 1st Earl Mountbatten of Burma.
Hypothesis: Edwina Ashley was the niece of Sir Ernest Cassel.