Season 1 ITV1 , 1973 Watch now Season 2 ITV1 , 1974 Watch now Season 3 ITV1 , 1974 - 1975 Watch now Season 4 ITV1 , 1975 - 1976 Watch now Season 5 ITV1 , 1977 Season 6 ITV1 , 1978 Season 7 ITV1 , 1978 Season 8 ITV1 , 1979