Anna Jordan is a highly talented young playwright who has never been attracted by the upper echelons of society. In in this play, which won the 2013 Bruntwood Prize for Playwriting and was first seen at the Royal Exchange in Manchester, she hits rock bottom, focussing not so much on the dispossessed as the never-possessed.
The opening scene is set in what looks like a badly maintained squat but is the Feltham home of half-brothers Hench and Bobbie, respectively 16 and 13.
We swiftly learn that the pair, played with impressively fearsome authenticity by Alex Austin and Jake Davies, have largely been abandoned by a mother who can only be in her mid-thirties and has been seduced by the questionable attractions of "minge-faced" Alan in an affair that does not seem destined to last.
Sian Breckin's Maggie is an alcoholic diabetic following an honourable tradition, as her own mother has disappeared too, swept off her feet by Slick Vic.
The borderline psychotic boys are a handful, having retreated from the world to experience a feral life with Taliban, a potentially murderous wolf-dog, as well as the ubiquitous PlayStation.
Their lives are execrable, Bobbie arguably having a worse time than in the "unit" from which he has escaped and in which he was incarcerated for undisclosed crimes.
While the depictions in Ned Bennett's traverse production are all too convincing, watching dead end kids behaving sadly and badly begins to pall, even when brightened by the occasional visit from scrounging mum.
The evening is brought to life with the arrival of another 16-year-old. Jen (the Yen of the title) is a recent Welsh immigrant with her own problems. Fresh-faced Annes Elwy's character is positively angelic, originally arriving to rescue and tame Taliban but swiftly switching her sights to Hench.
She manages to do a fine job of civilising that particular wild animal but, as every zoo keeper knows, it is rarely safe to turn one's back on the beasts of the field.
The final scenes set some time later are chastening and offer little hope for a society that can breed people like this, let alone for the characters portrayed whose futures all seem bleak.
While Anna Jordan shows in raw reality many of the problems that have led the boys (and to a lesser extent Jen) to such a predicament, she would have benefited from devoting a little more time to their back-stories and motivations, as viewers are left with a few too many gaps in their understanding of the underlying psychologies.
Even so, all four actors show their mettle, with each of the three youngsters excelling having been given the meatier roles, especially Annes Elwy.
Yen is a harsh play that takes time to ignite and very nearly comes off once it shows viewers what life can be like for the dregs of society in London today and why we should all work to ensure that no more families end up like this one.