(Spoilers ahead - be warned)
Absolutely fucking fantastic first episode! The twist before the credits rolled dragged you in nice and fast and the promise of a simultaneous expansion into the vicious gang politics of 1920s London and the politics of the Irish civil war should ensure that the series remains fresh.
Admittedly it seemed a bit cheesy that both Grace and Campbell survived the shooting incident at the end of the first series. We hadn't previously been given any evidence that Grace was the sort of double agent that would fail to finish off a dangerous and ruthless opponent. However, when it means that we get another series of three great central characters facing off against each other you can hardly bemoan the methods.
All in all I'm not sure that this episode could have been bettered. Let's hope the series shapes up well after this early promise!