DOCTOR: It's very interesting.

RANGE: It used to generate a basic form of energy, but we no longer have any fuel. This planet is without wood or any combustible material.

DOCTOR: What about the colony ship? Must have been brimming with gadgetry.

RANGE: Oh, systems that could rebuild a civilisation for us. Failure-proof technology.

DOCTOR: What happened to it all?

RANGE: It failed. And nothing survived the crash.

TEGAN: Come on Doctor, all these tunnels look the same.

DOCTOR: Oh but they aren't.