Fast twists and shifts complemented by distinct fight scenes
In many aspects, it is not an ordinary depiction of life in a Western capital and world city, and those not familiar may think that it is a place where you easily fall victim to any violence and crime... Thus, plenty of exaggerations, although different ethnic gangs do exist in London and over 100 people are murdered annually. But the story is in place, motives explained, characters seem realistic, and the performers used are not regular in British series (I think I know as I have seen hundreds of them this century :)). To me, the "older" generation excels the younger one -- I enjoyed the performances of e.g. Colm Meaney, Michelle Fairley, Asif Raza, Mark Lewis Jones most.
Well, the fight scenes are a kind of Evans´ trademark, not too realistic and not fun, but harsh and violent. A sharp contrast to non-agile London life and the scenes immediately preceding -- apparently not to everyone´s taste who sat to watch a British crime series, moreover, the shot or stabbed ones die slowly and "with style"...
Nevertheless, a good series, far better than using supernatural forces or comic book characters for solving crimes.