Premise: Till Death Us Do Part is a British television sitcom that aired on BBC1 from 1965 to 1975. The show was first broadcast as a "Comedy Playhouse" pilot, then in seven series until 1975. Six years later in 1981, ITV continued the sitcom for six episodes, calling it "Till Death...". The BBC produced a sequel from 1985 until 1992, "In Sickness and in Health".
Hypothesis: BBC did not air every episode.