Strong passions inflame Blue Story. A classic morality tale – a topical British riff on Boyz In The Hood - about two childhood best friends who are torn apart by gang warfare, it’s a lament, with narration eloquently rapped, for those killed and injured in the knife crime epidemic which has afflicted London’s poorer communities, impacting on black teenage boys in particular. It’s a film adaptation of writer/director/grime artist Rapman’s Youtube videos of 2014, made before Shiro’s Story brought him fame on the smallest screen. Not formally trained, Blue Story is Rapman’s - real name Andrew Onwubolu -  film school, a £1.3m, 75 percent BAME production backed by BBC Films and Paramount which has opened the doors to a cast of fresh faces and a brand new crew.

Thus Blue Story is an intriguing proposition: all that energy and raw talent poured into a highly conventional story with a rapped narrative delivered by the director himself, playing his own Greek chorus (this film is based in part on his childhood experiences). The film-making itself can stumble - this isn’t always a smooth watch; and such heartfelt sentiment sets it apart from more savvily sophisticated similar dramas. But there’s an appetite in the UK for a homegrown film like Blue Story, and it certainly hits a topical nerve.

Audiences will come in large part from those 18m-plus viewers of the three-part webseries Shiro’s Story. Yet even before that, the Kidulthood films (also driven in part by Damian Jones, who produces here), defied commercial expectations. Top Boy, now resurrected on Netflix and sharing a star in Micheal Ward, is drawing large audiences. In a country which has no real equivalent to – for example - the gritty multi-cultural French banlieu drama, all audiences should welcome Blue Story, and hope that its clearly commercial aspirations can blow a hole in the box office for others to follow. Plan B tried with Ill Manors. Expect lines for Blue Story in its South London home.

Two factors which help Blue Story gel are casting – both leads are equally magnetic – and that raw texture which Rapman brings to the streets of Peckham and Lewisham (another London borough substituted for the shoot, given the sensitive subject matter). And the roots of the story will be familiar to many British teenagers whose academically aspirational parents have sent them to a better school outside their own neighbourhood at a point in their lives where it could do them damage. That’s what happens to Timmy (striking newcomer Stephen Odubola), who is close friends – almost like a brother – with Marco (Micheal Ward, who plays Jamie in the Netflix Top Boy reboot, so it’s familiar territory for the actor). They both attend senior school in Peckham, but Timmy is from another borough – not good news when there’s a bitter postcode gang war in progresss.

Trouble starts to build when a childhood friend of Timmy’s beats up Marco outside his home turf: Marco’s aggressive brother Switcher (Eric Kofi Abrefa) is the leader of the Peckham gang, and he’s not happy about this slur. Meanwhile Timmy finds love with fellow GCSE student Leah (Karla-Simone Spence), but it all seems too good to be true. The close friendship between Timmy and Marco, laughing and messing around in the school’s recreational area wearing school ties and blazers, soon turns dark – literally, because these gangs are clad head-to-toe in black. That, plus the drawn-down hoodies which can obscure actors’ faces, can make gang identification a challenge, but Rapman gets the viewer there eventually.

A compelling, grinding soundtrack and spoken narrative drive home Rapman’s cautionary tale. Will Blue Story’s brand of modern inner-city Britishness prove exportable? With audiences overseas used to the comforts of Yesterday or Blinded By The Light it will certainly be a challenge, given the familiarity of the bones on which Rapman hangs his story, from Caine and Abel, down through Little Cesar and Boyz (or Juice). And the dialogue is heavy on the vernacular. Still, though, there’s something about Blue Story which is infectious. It might catch on. There’s a message in here, and if only the target audience shows up, Rapman’s job will have been done. Meanwhile, he seems destined for bigger things.