The Evil of the Daleks - S4-E9
Continuity mistake: (Animated version). Waterfield puts down the photo of the Doctor on his desk but the next time we see his desk the photo is no longer there and then later it's back on the desk again, without Waterfield having moved it.
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 ★