There's a poem by Norman MacCaig called Brooklyn Cop that tackles the question of what it must feel like to be a policeman who has to leave his house every day and face the risk of being hurt or killed.

"Who would be him," asks the poem, "gorilla with a nightstick, whose home is a place he might, this time, never get back to?"

In its own way, the new drama Good Cop (BBC One, 9pm, Thursday) asks the same question: can an ordinary policeman stay normal when he pulls on a uniform and faces serious physical risk every day? And what kind of mental damage is done to a man who knows he might at any moment, in MacCaig's words, "plunge through into violence"?

In Good Cop, the violence starts when PC John Paul Rocksavage (Warren Brown) and his colleague Andy Stockwell (Tom Hopper) answer a call about a disturbance at a house. Stockwell is badly beaten and it's as Rocksavage deals with that, and tries to wreak some kind of revenge, that his goodness starts to crack.

Warren Brown, who plays Rocksavage, is able to project the effects of this good/bad struggle extremely well and, even though he's a graduate of Hollyoaks, does it without any soap-opera histrionics. This is an ordinary man who has ordinary reactions; a man with storms in his head but only ripples on his face.

In his script, Stephen Butchard writes the words but also the spaces between the words. There are silences, pauses and some wonderfully long, slow scenes in which nothing much happens. I hope it's a riposte to the choppy, hysterical way most drama is shot. It might be the beginning of the end of attention-deficit TV.

In the meantime, we've still got three more episodes in which the most interesting strand of Good Cop can be developed. We can see what happens to Rocksavage. We can watch the effects of bad slowly seeping, like ink, into good. And we can think about the reality that's really the centre of this drama: policemen are the victims of violence but they hand it out as well. Or as Norman MacCaig puts it in the last line of Brooklyn Cop: "Who would be who have to be his victims?"