Lorna Arnold, née Rainbow, was born in Harlesden, then a village northwest of London, now part of Greater London. She won a scholarship to Bedford College, London, then trained as a teacher at the Cambridge Training College for Women, but left teaching in 1940. During World War II, she served in the War Office and then in the Foreign Office. There she headed a section of the secretariat of the European Advisory Commission, planning for the Allied control of Germany after the war. She served as a member of the British administration in Berlin just after it fell to the Allies in 1945, and engaged in difficult negotiations with the Russians, French and Americans. She continued her work for the Foreign Office with a posting to Washington, D.C., where she may have been the first female British diplomat. After returning to England, she married Robert Arnold, an American musician, with whom she had two sons. In 1953, her husband left her and went back to the USA, and she went back to work. In 1959, she joined the United Kingdom Atomic Energy Authority (UKAEA), where she worked within its Authority Health and Safety Branch, coordinating the investigation of the 1957 Windscale nuclear accident. She worked with and wrote about key scientists, engineers and administrators of the British nuclear civil and weapons programs, some of whom became her good friends. With Margaret Gowing, she co-authored a two-volume official history of the British nuclear weapons programs, Independence and Deterrence: Britain and Atomic Energy (1974). Other works included A Very Special Relationship: British Atomic Weapon Trials in Australia (1987) and her most famous book, Windscale 1957: Anatomy of a Nuclear Accident (1992). She was elected a Fellow of the Institute of Physics, a rare honor for a non-scientist, and the Institute of Contemporary British History. She was awarded the OBE in 1976. Even in old age, she was still an active participant in public debates on issues relating to nuclear energy and technology. In 2012, at age 96, she published her memoirs, My Short Century.