I think ultimately there isn’t one top dog / H / fourth man in the police force. There’s a number of separate OCGs that use high ranking police officers to help organise and cover up their activity, and if/when that officer is exposed, they move onto the next one, hence Buckells after Dot and Hilton and so on. There’s no one person pulling all the strings and it will keep happening because they’re always infiltrating OCG members into the police force that will rise over time. Carmichael/Osborne/Wise don’t want to admit there’s an institutional problem so ultimately nothing will stop these officers from rising as they just look at smaller individual corruption cases rather than the bigger network.
And that ending is fine. But why did the final episode still feel so flat and disappointing? They should have given us more explosive scenes like the shoot out earlier on. They should have made Buckells expose more of a sinister character at the end, or not included him in this series at all until the final episode so it was more of a shock, because when they held out from showing us who was going into the interview room... who else could it have been really? It wasn’t tense at all because we all knew it was him. They shouldn’t left so many loose ends... What did Carmichael do with Ted’s admission, was Kate working for AC12 all this time, is Lomax bent (although arguably I don’t mind that one being left open, as it backs up the point that officers working for the OCG will continue to rise).
The more I think about it, the more I’m OK with the ending, but it was so poorly executed that it almost makes it even more frustrating and disappointing than it should be?