So we know we’ve seen this face before. In “Deep Breath” the Doctor keeps talking about how he’s seen this face before, but he can’t remember where. He says something about how the regeneration always chose his face from faces it knew. The first time we see this face is when Ten learns that, at least in some capacity, time can be rewritten, that even though history says everyone in Pompeii died, he could save this family.
The Doctor said to Clara, at the end, “I’ve made a lot of mistakes….it’s time to do something about that.”
Is it possible that the regeneration chose that face to remind him of the fact that he could change those mistakes?
And if so, what does that mean about his previously regenerated faces?