Last night's viewing - Top Boy, Channel 4; Young Apprentice, BBC1

When I say that Ronan Bennett's Top Boy is half the drama The Wire was, it's meant as a descriptive remark not a critical one. On the evidence of its excellent first episode, Top Boy more than justifies Channel 4's decision to rearrange its schedules and run it through the week.

But, although The Wire provides one obvious model for what Top Boy sets out to do, with Baltimore's corners and crack houses replaced by their London equivalents, Bennett's focus turns out to be far tighter than that of the HBO series. Where that offered a 360-degree view of a city's power-bases, this concentrates only on the shadow economy of drugs in an inner-city neighbourhood – how the trade is staffed and run and how it finds its new recruits. It isn't interested in the standard cat-and-mouse game of a police procedural. It's a kind of sociology by other means.

It began with an odd image of detachment, as a young boy ate breakfast cereal while he looked down at a drugs raid from a tower block – a raid not by law officers but by a rival gang. The young boy is Ra'nell, not a player yet but already being eyed up as a runner by two low-level drug-dealers called Dushane and Sully with whom Ra'nell has a dubious kind of in. "Remember, you shanked up his dad last year," says Sully, as if a street knifing confers a kind of kinship. While Sully plays on Ra'nell's sense of filial duty to his depressive mother, Dushane offers him a clan: "Listen. We're your family now... think of all this lot as your cousins, yeah?" And since Ra'nell's mother has just been admitted to a psychiatric hospital, he's vulnerable to what looks like kindness.

He has other options: his friend Gem, a neighbour called Heather (who is setting herself up with a high-rise marijuana farm) and Leon, a reformed gang member who tries to ensure that Ra'nell doesn't slide into crime. One of the drama's central propositions, though, is that ambition doesn't have a lot of places to go in this society. "I was born and bred in Summerhouse. I'm 26 years old... I've got nothing else to be except this," says Dushane, when he's pitching for promotion to the area's criminal boss. It's a line that juts a little proud of the drama's surface. Does Bennett mean us to take it as evidence of Dushane's falsely narrowed horizons or is he putting a liberal plea of mitigation in his character's mouth? It feels forced, but it's an untypical moment of thematic subtitling. Elsewhere, the dialogue, slangy and offhand, doesn't worry if we don't entirely get it, and relishes the opportunity for very black comedy. In a horribly violent scene, Dushane and Sully cut off a man's finger as punishment, only realising too late that they've clipped the wrong one. Dushane insists they put things right: "Attention to detail, innit," he says.

Yann Demange's direction delivers a film that is both naturalistic and expressive, with casual underplayed performances from the young cast and heightened colours on screen. Ra'nell's flat is a composition of sickly greens, with even his mate's windcheater getting into the tonal act, while a nightclub scene with the drug boss is filmed in orange and medicine-bottle blue, simultaneously glamorous and unsettling. It doesn't look beautiful, exactly, but it's ugly in a very stylish way. And the drama it serves is already making a good case for its proposition that vice is exactly the right word – not just a moral judgement on how people behave but a description of the clamping circumstances that stop them breaking free.

"I take a relaxed approach to working," said Ben in last night's Young Apprentice, a line that made Lord Sugar's head snap up like a velociraptor scenting blood. It's a bit like Top Boy really – a powerful boss figure luring the young into a world where profit is the highest value and friendship is a liability. But we're meant to approve of these foot soldiers.