The Doctor: Unless we are prepared to sacrifice our lives for the good of all, then evil and anarchy will spread like the plague.
The Doctor: In all my travelling throughout the universe I have battled against evil, against power mad conspirators. I should have stayed here. The oldest civilisation: decadent, degenerate, and rotten to the core. Power mad conspirators, Daleks, Sontarans, Cybermen, they're still in the nursery compared to us. Ten million years of absolute power. That's what it takes to be really corrupt.
(The Master's image appears on the screen)
The Doctor: Oh no, now I really am finished!
Mel: Who's that?
The Doctor: Just one of my oldest enemies.