[Well, a little bit of appreciation would be nice, what with saving their entire species from extinction and all. He looks a little crestfallen at the Master's suggestion; the Doctor's always been a bleeding heart.]

No. There'd been enough deaths in the Time War, enough planets destroyed in the wake of civilisations clashing. I couldn't let it happen again.

[He thinks about saying something when the Master turns his back on him, but he realises it's probably better to let him go. Their conversations work best when kept as short as possible, and this one has already gone on too long.]