In a story that has been full of classic scenes, Episode Five gives us the first one-on-one confrontation scene between Davros and The Doctor, including the magical moment when Davros questions whether or not he would use a poisonous vial to wipe out all life (answer: yes).
The whole scene doesn't play out as two rivals arguing, or a captor continuing an interrogation of his prisoner, but, as Davros states, as a meeting of two premium scientific minds. Watch how Davros shoos his guards, including his right hand man, Nyder, out of the room, so that it's just Davros, a withered man in a wheelchair, and The Doctor, alone in the room. The Doctor could quite easily overtake Davros (which he finally does towards the end of the scene), but chooses not to, because, like Davros, he is fascinated by the scientific debate. It hearkens back to the almost cordial relationship The Doctor had with The Master in stories like The Mind of Evil and The Claws of Axos, which saw two enemies united, however briefly, in the cause of science.
And how about that cliffhanger? The Doctor being in obvious distress while being strangled by a Dalek mutant is one thing, but it's quite another for David Maloney to shoot the scene with alternating, graphic close-ups. Many a child in the UK was have been spooked to tears after having those images stuck in their brains for the week to come. This is truly the age of "behind the sofa" viewing in Doctor Who.