I can’t decide between The Sea Devils and The Curse of Peladon. The latter is an epic, wonderfully acted and very atmospheric dialogue-heavy monster-fest, while the former is my first real memory of Doctor Who.
I can’t get over how expensive these two serials looked - some excellent studio sets and model work from Ian Scoones (on film, as well, as opposed to videotape), lovely monster costumes for Peladon and similar stuff, and a lot of lovely-looking locations for The Sea Devils. But which to choose?
With a nod to the clever and intriguing Day of the Daleks story, I’ll put The Sea Devils in first place.