Jean, on the right in the tall hat

Roy Herrick, a versatile TV actor in the 1960s and 1970s, was first seen in Doctor Who in 1964, as Jean, who saved people from the Guillotine in Reign of Terror. In 1977, he was the voice of the schizophrenic computer, Xoanon in The Face of Evil and then Parsons, Professor Marius's assistant, in Invisible Enemy.

Xoanon the Schizophrenic Computer

Parsons