Hampshire's work in feature films is less well-known to American audiences. After an appearance as a child in the British-made "The Woman in the Hall" (1947), she appeared in ingenue roles beginning with "Upstairs and Downstairs" (1959). She was the mother in "The Three Lives of Thomasina", a 1963 Disney film about a girl in a Scottish village who heals animals through love. Her career transformed when she starred in Pierre Granier-Deferre's "Paris in the Month of August/Paris au mois d'Aout" (1966), in which she appeared in a nude scene. Hampshire later married Granier-Deferre (they divorced in 1974). Her portrayal of African-based naturalist Joy Adamson in "Living Free" (1972), the sequel to "Born Free" in which Elsa the lion has died, received some notice in the States. Some of her other appearances in film, including her work in several French films are almost unknown to US audiences.

Hampshire's work on stage in England began in the late 50s, and has included Shakespearean interpretations, from Rosalind in "As You Like It" to Katherina in "The Taming of the Shrew" (both at the Shaw Theatre). She played Peter Pan in a 1974 production of the classic musical as well. For most of the 80s, her performing career was virtually inactive. Hampshire devoted herself primarily to writing gardening and children's' books, including the "Lucy Jane" series. She authored "Susan's Story" (1982), which recounted her struggle with dyslexia, and "The Maternal Instinct" (1985), about coping with her daughter's fatal illness. Hampshire returned to the theatre in a 1990 production of "A Little Night Music" and was on stage at the Savoy Theatre in London in "Relative Values" (1993).