RACHEL: Why are two Dalek factions fighting each other.

DOCTOR: Ace.

ACE: It’s simple, isn’t it. Renegade Daleks are blobs.

DOCTOR: Blobs?

ACE: Imperial Daleks are bionic blobs with bits added. You can tell that Daleks are into racial purity. So, one lot of Daleks reckon the other lot of blobs are too different. They’re mutants. Not pure in their blobbiness.

DOCTOR: Result?

ACE: They hate each other’s chromosomes. War to the death.