SARAH: But they lost. You know, the worse the situation, the worse your jokes get.

DOCTOR: Therefore, if I've guessed correctly about the nature of Helix energy, I should be able to drain it off.

SARAH JANE: But what if you've guessed wrong?

DOCTOR: When did I ever guess wrong about anything?

SARAH JANE: (sotto) Lots of times.

SARAH: Just how big is the TARDIS?

DOCTOR: Well, how big's big? Relative dimensions, you see. No constant.

SARAH: That's not an answer.

DOCTOR: How big are you at the moment?

SARAH: Five four, just, and that's still not an answer.

DOCTOR: Listen, listen. There are no measurements in infinity. You humans have got such limited little minds. I don't know why I like you so much.

SARAH: Because you have such good taste.

DOCTOR: That's true, that's very true.

SARAH: So what was going on back there in the temple?

DOCTOR: Sub-thermal recombination of ionised plasma.

SARAH: Oh, simple. I should have thought of that.