Revealing mistake: The Filer vs. Filer fight in the lab is very amusing, not only because of the several glimpses of the stuntman doubling for Filer, but also because of the way the "metal" railings around the set wobble as they slam into them.
Revealing mistake: In the UNIT tracking room, there is a flimsy railing behind the radar operators that Chinn knocks as Yates leads him off to the "direct" phone line, causing it to wobble badly. The Doctor then deals the railing another blow as he comes up to look at the console.
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 ★