Born in Arundel, Sussex, in 1948, Judy's father relocated the family to London when she was 10 years old, subsequently enrolling her and her sister Sally Geeson into the Corona Academy, Chiswick. Initially, Judy had aspirations to become a ballet dancer, but unfortunately, she was forced to alter her course due to the severe headaches she experienced as a result of certain dance moves. Acting had always been a significant interest of hers, so she decided to pursue this alternative, making her first television appearance in Dixon of Dock Green (1955) at the tender age of 12. Her first major film role was as a wayward teenager, Pamela Dare, opposite Sidney Poitier in To Sir, with Love (1967),at the age of 18.
After a remarkably successful film run during the 1960s and 1970s, Judy embarked on a trip to the United States in October 1984, ultimately deciding to stay for an extended period. By May 1985, she had met and married Kristoffer Tabori, subsequently relocating to California. However, the marriage had deteriorated by 1989. Despite this, Judy chose to remain in the United States, eventually making her home in Los Angeles.