The Trial of a Time Lord 13-14 (aka The Ultimate Foe) - S23-E4
Revealing mistake: In the final episode, Glitz and the Master leave the console room while the Doctor is driven into submission, but they are quite obviously standing by the scanner screen.
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 ★