She played the part of Jo from 1971 to 1973 alongside Jon Pertwee's incarnation of the Doctor. Manning struck up an immediate rapport with her co-stars, Pertwee, Nicholas Courtney (The Brigadier), John Levene (Sergeant Benton), Richard Franklin (Captain Mike Yates), and Roger Delgado (the Master). Fans of Doctor Who often refer to these characters as the UNIT family — UNIT, the United Nations Intelligence Taskforce, being the fictional United Nations squad that the Doctor worked for. Manning moved to Australia and was also seen in a famous Ruby Wax segment with longtime childhood friend Liza Minnelli.
Manning's connection with "Doctor Who" continues: She voices Jo Grant in the Companion Chronicles Audio Adventures, and she is also the voice of the Time Lady Iris Wildthyme in several of the Big Finish Productions audio plays. In 1978 she aroused controversy when she posed naked with an original Dalek prop for the glamour magazine Girl Illustrated. In 2005 Manning also appeared in Doctor Who - Inside The TARDIS with two of the doctors, Sylvester McCoy and Colin Baker, where they spoke of their experiences with the long-running show.