Season 1 BBC One , 1969 Season 2 BBC One , 1971 Season 3 BBC One , 1972 Season 4 BBC One , 1974 Season 5 BBC One , 1975 Season 6 BBC One , 1976 Season 7 BBC One , 1976 Season 8 BBC One , 1977 Season 9 BBC One , 1978 - 1979 Season 10 BBC One , 1996