Season 1 ITV1 , 1971 Season 2 ITV1 , 1971 Season 3 ITV1 , 1972 Season 4 ITV1 , 1972 Season 5 ITV1 , 1972 Season 6 ITV1 , 1973 Season 7 ITV1 , 1974 Season 8 ITV1 , 1979 Season 9 ITV1 , 1979 - 1980 Season 10 ITV1 , 1984 Season 11 ITV1 , 1985 Season 12 ITV1 , 1992