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Paigntonian - // All truly awful. Can I add Steptoe and Son, Jimmy Tarbuck, Last of the Summer Wine, Cannon and Ball, Little and Large. //
You can add all of those, with the exception of Steptoe And Son.
The essence of any great comedy, is that the protagonists are trapped in their world, and kick against it - that includes Fawlty, Hancock, Meldrew, and of course the Steptoes.
The earliest shows were shot in one take on one camera, just them in the living room, Harold desperate to escape, Albert desperate to stop him, Harold always giving in.
That was the tv equivalent of a stage play - start to finish, live, no edits, no re-takes, just acting out the claustrophobia.
But another golden ingredient of great sit com is pathos, and it needs to be just below the surface, and shown in flashes of tragedy in a blink-and-you-miss-it style.
That's where Wilfred Bramble scored - he could go from snarling selfish disgusting old man, to a look straight at the camera with the face of a frightened child, and back again so quickly you could easily miss it, but the impact was always there if you saw it.
So I have to argue for Steptoe And Son, groundbreaking in dialogue, concept, and presentation.