Ventham played Colonel Virginia Lake in the 1970s science-fiction television series UFO and had a recurring role as Cassandra Trotter's mother Pamela Parry in the sitcom Only Fools and Horses between 1989 and 1992.
Ventham's numerous other TV credits include regular roles in Heartbeat as Fiona Weston, Hetty Wainthropp Investigates as Margaret Balshaw, and in Series 2 and 3 of The Rag Trade as Shirley.
She has appeared in Doctor Who on three occasions over three decades; as Jean Rock in The Faceless Ones (1967), as Thea Ransome in Image of the Fendahl (1977) and as Faroon in Time and the Rani (1987).
Her appearance in Image of the Fendahl was opposite Denis Lill, with whom she would later act when they were cast as Pamela and Alan Parry in the sitcom Only Fools and Horses (1989–1992).
[11] She met actor Timothy Carlton in 1970 while filming sequences for the drama series A Family at War[4][12] and they have been married since April 1976.