Black was born in Emsworth, Hampshire. After attending Portsmouth High School for Girls, she studied psychology at London University. She had taken a number of jobs, including working in a local psychiatric care home. After graduating, she travelled to Gibraltar and later the West Indies, where she decided she wanted to become an actress. Her first professional role was as a cat in "Miniatures" at Sheffield's Crucible Theatre. She worked in several fringe theatres before gaining her Equity card in 1980. Black joined the Actors' Touring Company and performed Shakespeare around South America and in Israel, Greece and Yugoslavia.