Anita Leslie, born in New York City, was the eldest of three children of a wealthy Anglo-Irish landowning family. Her parents were Sir John Randolph Leslie, 3rd Baronet, known as Shane Leslie, a first cousin of Winston Churchill, and his wife Marjorie Ide. She spent her childhood in the 1920s between their estate in Ireland, a house in London, and schools and convents in various parts of Europe.
During World War II, she volunteered as a mechanic and ambulance driver for the Mechanised Transport Corps and served in Egypt, Lebanon, Syria, and Jordan. She also drove ambulances with the Free French Army in northern France in 1944-1945, and was awarded the Croix de Guerre. After a brief first marriage to Paul Rodzianko, in 1947 she married William King, a former Royal Navy officer, with whom she had two children. She and her husband took up farming and were avid fox hunters. The couple lived at Oranmore Castle, a 15th-century Norman keep on Galway Bay, Ireland. She wrote a biography of her grand-aunt Jennie, Lady Randolph Churchill, based largely on family papers and discussions with her grandmother, Leonie Jerome Leslie, who was Jennie's sister. Her 14 books also included biographies of Sir Winston's grandfather, Leonard Jerome; Churchill's son, Randolph; Mrs. Fitzherbert, mistress of King George IV; Madame Tussaud; and Francis Chichester; as well as Edwardians in Love (1972). Her autobiography, The Gilt and the Gingerbread, was published in 1981.