Doctor Who episode 417: The Android Invasion – Part Four (13/12/1975)
In practice the android invasion is confined to about two rooms in the space centre. This certainly has all the elements of a climactic episode – stuff that in theory should be fairly solid. Tom Baker playing an evil duplicate of himself and the two versions getting to fight, with the benefit of seven years of editing and effects evolution since Barry Letts last had a go at directing a scene like this in The Enemy of the World. Sarah Jane finally getting back to Britain in 1980, and being reunited with her friends Harry and Benton and (checks notes) Colonel Faraday.