Barbara: Oh, don't you see? If I could start the destruction of everything that's evil here... then everything that is good would survive when Cortez lands.
The Doctor: But you can't rewrite history! Not one line!
Susan: Barbara, the high priest is coming.
The Doctor: Barbara, one last appeal: what you are trying to do is utterly impossible! I know, believe me, I know!
Barbara: Not Barbara, Yetaxa.