He was the longest serving director on the original series of "Doctor Who" (1963), directing episodes over a duration of 16 years between 1963 and 1979. He was also one of only three directors (the others being Douglas Camfield and Lennie Mayne) to direct episodes starring all of the first four actors to play the Doctor in the series (William Hartnell, Patrick Troughton, Jon Pertwee and Tom Baker).
In 1974 he became the first person to direct a Dr Who serial ("Robot") recorded entirely on videotape.