Even though Keira Knightley and Ben Whishaw are the two least physically convincing killers ever seen on screen. Pretty sure the average deacon weighs as much as both of them combined. Some of the logic and plotting is a little suspect, but good actors and generally great writing. I'd watch a spinoff following the Irish assassins.
By the guy who did Giri/Haji, which was excellent.
Very Christmasy, though in setting rather than spirit. And only 6 episodes — little of the padding that slows down too many streaming shows.
Better than Slow Horses IMO — probably comparable in a lot of ways, but jumps between characters far less, which keeps it more focused and engaging.