Terror of the Zygons

FORGILL: I underestimated his intelligence, but he underestimated the power of organic crystallography.

DOCTOR: Yes, that's the TARDIS. And I'm going to pilot it all the way to London. I can be there five minutes ago.

SARAH: Just a minute, Doctor. I thought you couldn't do that.

DOCTOR: Of course I can. Coming?

BRIGADIER: No, thank you.

HARRY: I think I'll stick to InterCity this time, Doctor.

DOCTOR: Sarah?

SARAH: Er.

DOCTOR: No?

SARAH: All right. Providing we do go straight back to London.

DOCTOR: Oh yes, we will. I promise.

DOCTOR: When I left the psionic beam with you, Brigadier, I said it was only to be used in an emergency!

BRIGADIER: This is an emergency.

DOCTOR: Oil, an emergency?! Ha! It's about time the people who run this planet of yours realise that to be dependent upon a mineral slime just doesn't make sense.