Lady Irene Mountbatten (nee Lady Irene Dennison), first Marchioness of Carisbrooke GBE (1938), wife of Alexander Mountbatten (Princess Beatrice's eldest son), 1st Marquess of Carisbrooke, GCV GCVO and also sister of Hugo Denison 4th Earl of Londesborough. Also mother of Lady Iris Mountbatten.
Vanity Fair: The Mountbatten Sisters-Lady Pamela Hicks (standing) and her elder sister Patricia, Countess Mountbatten of Burma, only daughters of Lord Louise Mountbatten, 1st Earl Mountbatten of Burma and his wife the former Lady Edwina Ashley-fascinating interview with them about Lady Pamela's new memoir Daughter of Empire: Life as a Mountbatten.
Photos (clockwise from top left): Edwina Mountbatten, Countess Mountbatten of Burma; Penelope Knatchbull, Lady Brabourne; Penelope Knatchbull, Lady Brabourne; tiara detail; Patricia Knatchbull, 2nd Countess Mountbatten of Burma
Edwina Mountbatten, Countess Mountbatten of Burma, was infamous for her flagrant adultery