Ann de Trafford was born in 1918 in London, the eldest daughter of millionaire racehorse owner Sir Humphrey de Trafford, 4th Baronet, and the Hon. Cynthia Hilda Evelyn Cadogan, a daughter of Henry Cadogan, Viscount Chelsea. The de Trafford Baronets descended from a pre-Conquest-founded line of lords of the manor who were wealthy in the Middle Ages and whose titles were reinstated in the mid-19th century due to recusancy — a term coined to describe the minority of English who remained Roman Catholic during and after the Reformation in a time of significant religious persecution. Ann (later Dame Ann) continued to adhere to the religion of her family, Roman Catholicism.