Revealing mistake: In a few UNIT stories you can see where BBC TV badges have been on the UNIT land rovers.
Other mistake: In every William Hartnell title scene there is a point where it tells you that you are watching "DOCTOR OHO". It lasts for three seconds and is probably the result of a lazy FX team as the left side is a mirror image of the right.
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 ★