Tom Baker was unwell during filming. He and Lalla Ward were also not on speaking terms, after Ward rebuffed his attempts to rekindle their romance some weeks earlier.
Matthew Waterhouse did not get along with Tom Baker and Lalla Ward. He felt his costars were intimidating (he claimed that when he tried to say hello to Baker, he was told to piss off), while they found the neophyte actor to be impertinent and disrespectful at times, refusing to follow the instructions of cast and crew with vastly more experience than he.
For the only time during his tenure as the Doctor, Tom Baker had to have his hair permed before filming commenced. It had lost its natural curl due to the actor being in ill-health.
Subplots involving townsfolk nocturnally wandering the forest like zombies, and rebellious citizens being found with bat-like bite marks on their necks were removed from the script.