British show - Five seasons. Starts off as a wise-cracking undercover cop, then moves to much more dramatic in the 3rd, 4th, and 5th seasons.

The first season was ok, the second was awful. But the switch to drama in the 3rd season was one of the best seasons of TV I have watched. The 4th and 5th were pretty good, but just shy of the 3rd.

The 3rd season reminded me a lot of The Shield, my all-time favorite show.