Was John Cleese supposed to do a cameo?
Episode 6 of Season One ("The Return of the Speckled Band") has a long scene between Victor and "the electricity man," who has come to read the meter and loses his shoes in the process. I suspect the part of "the E.M." was written for John Cleese and that Cleese for some reason was unable to play it, because it is played by an actor (Clive Mantle) who is the spitting image of Cleese and delivers the lines with the same acidity as Basil Fawlty (Cleese).
Take another look at that segment and tell me if you agree with me. The similarity between Mantle and Cleese, in terms of physical appearance and delivery, is uncanny.