The Brexiteer's refrain – 'Take Our Country Back – is cleverer than it looks. It asks for control, but it appeals to nostalgia. Underneath the surface, it's a call to turn back the clock. Take our country back, back to better days. Years of Sunlight does just that. By rewinding to the halcyon days of the post-war welfare state, when new towns were springing up around the country, Michael McLean focuses our attention on its subsequent decline.

Set in Skelmersdale, an overspill town on the edge of the Liverpool, Years of Sunlight works backwards. As in Harold Pinter's Betrayal, three lives run in reverse, so that a story that starts with a charred body pulled from a burnt-out building tracks back 30-odd years through the dead man's life, all the way back to the sunny, carefree days of his childhood.

Emlyn (Bryan Dick) was a lifelong addict, raised in care and always somewhere resentful of the fact. As the years roll back, he seems to clean up his act. The bruised and bloodied thirtysomething, dependent on methadone handouts from the state, was once a young artist desperately trying to find his feet and, before that, a boisterous child swigging Batman cocktails of orange and lemonade on holiday with his best mate Paul (Mark Rice-Oxley).

At every stage of his life, Emlyn leans on Paul's mother Hazel (Miranda Foster), an Irish emigrant who hoped for a new start in Liverpool and found herself shunted on to ‘Skem,' a community she neither chose nor fits. Depending on your point of view, she either supports Emlyn or indulges him – a relationship that mirrors the welfare state. McLean's play gains from seeing both sides of state handouts.

One moment embodies the whole. As a sober, young artist, Emlyn hosts an exhibition and while Hazel offers to buy a painting, Paul invites him to Ireland. One offers a lump sum, the other, ongoing support – two different models of welfare, a one-off leg-up in life or continuing care. McLean suggests the spirit that built the new towns let them slide into disrepair; their fresh paint fading after years in the sun.

Investing in infrastructure is nothing without investing in people. For one thing, it's unchanging and, in the figure of Hazel's boorish, bullying partner Bob (John Biggins), a Manns Ale man, McLean suggests that the new towns were very much products of their time – designed by men, but inhabited by families.

It is, ultimately, too slight a story to bear the weight of 30 years of social history, but that's not to say Years of Sunlight isn't a touching portrait of a lifelong friendship. Theatrically, the play keeps us guessing, holding key details back as it rewinds, but, for all the tenderness of Amelia Sears's production, it's not entirely convincing. Despite shape-shifting performances from Dick and Foster, the years falling off them rather remarkably, McLean's characters seem more like metaphors for Skelmersdale's decline than credible products of it.

Years of Sunlight runs at Theatre503 until 18 February.