She was born Frances Ruth Roche in Park House, on the royal estate at Sandringham, Norfolk, on 20 January 1936. Her father was Maurice Roche, 4th Baron Fermoy, a friend of King George VI and the elder son of the American heiress Frances Ellen Work and her first husband, the 3rd Baron Fermoy. Her mother, Ruth Roche, Baroness Fermoy, was a confidante and lady-in-waiting to Queen Elizabeth (later the Queen Mother). Since birth, she held the style of The Honourable as the daughter of a baron.