9. Telling Sarah-Jane That He Would Come Back
There is some contention over this one, as technically the Doctor never actually promises to return to see Sarah-Jane Smith at the end of The Hand of Fear. With the events with Eldrad finished, Sarah-Jane is so frustrated with the Doctor that she storms out of the control room, demanding to be taken home. None of this is meant seriously but, while out of the room, the Doctor receives a telepathic summons from Gallifrey.
'I can't take Sarah-Jane,' he says to himself, leading to some very emotional farewells not long after. As the two friends part ways, they implore each other not to forget each other. 'Til we meet again, Sarah,' he says before the TARDIS dematerializes.
It's fairly safe to say that this was meant literally, though there really isn't a time limit on that. Nor, in fact, does time move normally for a Time Lord with a TARDIS. It also seems that the TARDIS prevented their reunion, as on his next trip to London he ends up in the wrong location, though he does gain a new companion.
This may be somewhat of a stretch to include this. Perhaps this should be marked as an unintentional lie that the Doctor told, though it did cause poor Sarah-Jane years of fear and doubt.