[Tyson]

Other than perhaps The Walking Dead, I can't think of another TV show with such a ferocious appetite for killing off major characters as Spooks had. Sorry, can't bring myself to call it MI-5. Just can't...

D.D.

Game of Thrones is the only show even close to these 2 in that aspect.

[wndrmke]

+1 for Wire in the Blood, Cracker & Luther.

One that so far has not been mentioned; The Vice (1999 - 2003) is worth seeking out.
 
Portishead's Sour Times was the theme song and I have to give the show credit for steering my music journey in a new direction.

[oldmp3]

Broadchurch on BBC America: http://www.bbcamerica.com/broadchurch/. Also Amazon Instant Video:

BBC AMERICA’s “Broadchurch,” which earned critical acclaim, including BAFTA nods, and broken records on Twitter in the UK, centers on the investigation into the murder of a young boy in a British seaside town.

[Chazro]

+1 on Broadchurch!  AND the amazing 'Luther' returns in Sept.  Albeit for a painfully short 4-episode season.