Amiel was born into a Jewish family in Watford, Hertfordshire, England, the daughter of Vera Isserles (née Barnett) and Harold Joffre Amiel. A cousin was the oncologist, broadcaster and humorist Rob Buckman. Her father, originally a solicitor, became a Lieutenant Colonel serving in Italy during the war, but was discharged because of injury. Her parents divorced when she was eight, after her father left her mother for another woman. Amiel attended North London Collegiate School in Edgware, Greater London, an independent girls' school.