I began with series 4 which I mostly watched on BBC2 but didn't watch all of series 5 this year because of other commitments. I have seen series 1 and 3 which I found quite nasty and boring in places and there was a bit too much nudity but I'm on 2 at the moment and it's ok. It's obviously a UK version of Boardwalk Empire but Cillian Murphy is a very strong, charismatic and uncompromising presence, giving some depth to the ruthless Tommy Shelby and there are two strong female characters in Ada & Polly. Very cinematic in scope as it's made in widescreen, there is a lot of intrigue and excitement plus action in the plots and the soundtrack is superb.