The Fearmonger

ACE: Oh, "No coloured" signs in 1963, "Pakis out" and petrol bombs in my time - now it's the future and it's ethnic cleansing. Nothing changes, does it?

DOCTOR: Forty years ago, Harper wouldn't even have been out of the ordinary. It does change, you know. Never completely, never all at once, but it does.

ACE: But when?

DOCTOR: Are you looking for the butterfly?

ACE: What the one who beats its wings and tips the balance, so the hurricane forms? There isn't one, is there?

DOCTOR: Not often. They just tell the butterflies that to keep them happy.

ACE: I should have known.

DOCTOR: No, mostly they break the butterfly on the wheel of time. But over the decades, the millions of butterflies, the weather still changes somehow. That's time. A million, multi-coloured pieces of time.

ACE: You could turn it all around you know, reach your hand in and just... well, change everything!

DOCTOR: Yes. But then I'm a silly old man, with far too much time in his hands already.

“This is ridiculous! How can you go from plenty of time to running out of time in no time at all?”

DOCTOR: Paul Tanner, congratulations, you're today’s lucky winner. Ace, tell the man what he’s won.

ACE: A complete set of explanations from the Professor here. And you have no idea what a rare and precious thing that is.

DOCTOR: Do you want a dangerous fugitive staying in your flat?

PAUL: Of course not.

DOCTOR: Well then, don’t upset him and he'll be a nice fugitive staying in your flat.

DOCTOR: You might want to break the window first.

WALTER: Doctor!

DOCTOR: After all, if it just bounces off the glass, well, fire-bombing her petunias isn’t much of a statement.