Cast in the role of Davros was Michael Wisher, who had previously appeared in several different roles on "Doctor Who" and had provided Dalek voices in the serials "Frontier in Space", "Planet of the Daleks" and "Death to the Daleks". Wisher based his performance as Davros on the philosopher Bertrand Russell. In order to prepare for filming under the heavy mask, Wisher rehearsed wearing a paper bag over his head. Friedlander's mask was cast in hard latex, with only the mouth revealing Wisher's features; make-up artist Sylvia James shaded the mask's tones and blackened Wisher's lips and teeth to hide the transition.