Deliberate mistake: Tom Baker has some wounds on his lip (caused by actor Paul Seed's dog) which appear in episode one and four in the TARDIS scenes and disappear for the rest of the episode.
Deliberate mistake: The shot of rocks falling in episode four is used twice - once when Unstoffe is shot, once after the captain fires the cannon.
Answer: TARDISes are generally available for properly authorised use on Gallifrey; they're not usually assigned to a particular Timelord on a long-term basis. The Doctor stole his when he left his homeworld.
Tailkinker ★