At the end of Utopia the Doctor Locks the controls Permenantly so the Master can't travel back past 2007 but in Later Episodes he goes back to Pompeii in 79AD! So how could he have un-deadlocked the controls?
Apparently you missed the episode right after that one, where at the end everything on earth goes back to the way it was before the tardis was taken over by the Master. I would assume that the tardis went back to normal, since it had been turned into a paradox machine and in the later episodes it is the tardis again. So the controls would be unlocked.
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