Lady Mary Katherine Pakenham was a daughter of Brigadier-General Thomas Pakenham, 5th Earl of Longford, who was killed in World War I when she was a child, and his wife Lady Mary Child-Villiers. Five of the 6 siblings in the family grew up to become writers. She grew up in London, at North Aston Hall in Oxfordshire, and at Pakenham Hall, their Irish home. She had the usual education of girls of her class with governesses and two terms at a domestic economy school, before making her debut in society. Having come into a small income at age 21, she took a trip around the world and on her return to England embarked on a career in journalism. She worked with her younger sister Violet at the London Evening Standard, writing a weekly article about fashion and "intelligent" gossip. Under the pseudonym Hans Duffy, she published four novels between 1932 and 1937, and wrote for the comic weekly Night and Day. She wrote an affectionate memoir, Brought Up and Brought Out, published in 1938 and Christmas With the Savages (1955), based on family gatherings. She also wrote biographies of Caroline Clive (1949), John Donne (1966), and King Edward IV (1973). In 1940, she married Meysey Clive, an army officer and landowner, and lived at Whitfield, his large family home in Herefordshire. Her husband was killed in action in 1943 during World War II, and she brought up their two children alone in Rabbit Cottage, the head gardener's house on the estate. After the war, Lady Mary Clive improved Whitfield and entertained friends and fellow writers. She was close to her sister-in-law Elizabeth Longford, the historian and biographer, and they often took research trips together.