The son of Jasper Maurice Alexander Ridley (1913-1944), by his marriage to Helen Cressida Bonham Carter, a daughter of Sir Maurice Bonham Carter and Violet Asquith (herself a daughter of the British prime minister H. H. Asquith), Ridley lost his father during the Second World War.
He is a first cousin of the actress Helena Bonham Carter and a more distant cousin of the Conservative cabinet minister Nicholas Ridley and the historian Jane Ridley [REF].