After joining the BBC in the late 1960s, Grimwade first worked on Doctor Who as a production assistant on Jon Pertwee's first serial, Spearhead from Space (1970).
[3] George Gallaccio, producer of The Omega Factor (1979), gave Grimwade his full directorial debut on the episode "Out of Body, Out of Mind" in the series.
Prior to this, Grimwade had written two serials, Time-Flight (1982)[5] and Mawdryn Undead (1983),[8] and had been asked to write Davison's penultimate story, which became Planet of Fire (1984).
Because the story's requirements were in constant flux, mainly due to uncertainty over the filming location and cast changes, he eventually became frustrated and allowed script editor Eric Saward to finish the serial.
Although Planet of Fire transpired to be Grimwade's final work for Doctor Who, on 13 August 1984 he was commissioned by Saward to write a four-part story entitled The League of the Tancreds.
The play was about events behind-the-scenes on a low-budget science fiction television series, which Grimwade openly acknowledged was inspired by his experience working on Doctor Who.