He joined the show at the start of Season 18, succeeding Douglas Adams as script editor. At the same time, John Nathan-Turner took over from Graham Williams as producer. Bidmead and Nathan-Turner had a very different take on the show from their predecessors, seeking to reduce the comedic and fantastical elements that had dominated the previous era and root the show more firmly in reality, with more hard science and a more serious tone.
This new approach led Bidmead to rewrite and make changes to many scripts that had been originally written with the previous regime's tone in mind, for example the season's opening story "The Leisure Hive" by David Fisher, which had originally been envisaged as a comedic paradoy of gangster movies.
Bidmead wrote three Doctor Who stories himself: the Season 18 finale and Tom Baker's regeneration story "Logopolis", the following season's opener and Peter Davison's debut "Castrovalva", and "Frontios" in Season 21.