I mentioned Line of Duty in the Dublin Murders thread and just finished the fifth season. Outstanding series. Truly an all-time great show, especially for those who like police procedurals. With the seasons being either 5 or 6 episodes long, it cuts out a lot of the filler and crap that dilutes other similar series. It's all meat without overused tropes. Completely devoid of flash and style. Kind of refreshing, really. Line of Duty focuses on police corruption from the perspective of an anti-corruption agency. Great writing. Solid acting. I won't spill a minor spoiler, but I'll just say that after one season ends, you want to start the next one pretty soon. Also, Line of Duty was created by the same guy (Jed Mercurio) who created and wrote Bodyguard, which most here liked quite a bit. If you liked Bodyguard, you'll certainly enjoy Line of Duty. Can't wait for the sixth season. https://www.imdb.com/title/tt2303687/
Good. The second season is better than the first. If you're at all on the fence during the first season, watch the second before making up your mind. The police interrogation/interview in episode 5 (of the second season) is the best I've seen in a police drama. Awesome episode. One tip is to select subtitles. Otherwise, you can miss a lot due to accent and lingo. Another is to know the police abbreviations: DI, DS, DC, DCI, DCC, etc.