Alfred Hitchcock once said that the length of a film should be directly related to the endurance of the human bladder. At a little over two hours and thirty minutes, Chris Urch’s first full-length play requires a bit of patience and a strong bladder, but its longer running time is wholly necessary to what it is trying to achieve.

First seen at Theatre503 in September last year, Land of our Fathers is set on the eve of the 1979 general election and concerns six Welsh miners trapped underground, after an electrical explosion causes a tunnel to collapse above their heads. At first spirits are high, with the group happy to while away the hours rationing out packed lunches and filling in crumpled crosswords, safe in the knowledge that those above ground are doing their level best to rescue them. But as hours turn into days, days into weeks, the desperate reality of the situation begins to dawn on the trapped miners.

For much of the play’s first act, you’d be forgiven for forgetting the evident danger of the situation. The action is breezily paced and brilliantly funny, with Urch revealing himself as a writer with a particular pennant for punchy one-liners – many of which are far dirtier than the miners’ mud-covered faces. But not only is this one of the best written and funniest débuts you are likely to see, it has a tonal variation rarely found in the work of first time playwrights, with the lewd laughter of the first act superseded by surprising darkness in what is a necessarily bleaker second act. In one sequence, as the effects of dehydration take hold, the previously upbeat Curly (Kyle Rees) recalls a disturbing dream from the night before. Accentuated by Simon Slater’s otherworldly sound design, Urch locates a dense poetic surrealism that brings to mind the work of Philip Ridley and the late Sarah Kane.

Paul Robinson’s production does well to emphasise the richness of the writing, revelling in the laughs and set pieces as much as the moments of intimacy and increasing intensity. He draws out impressive performances from his excellent cast, with Patrick Brennan playing the deputy Chopper with all the unbridled force of a wardrobe falling down a flight of stairs.

Though some might protest that the play is overly long, its length is integral in establishing a feeling of endurance on which the play relies. If it had been restricted to 90 minutes, much of the character ambiguities and tonal complexities would likely have been hammered out. As it is, this is a distinct début from an outstanding new voice.

Land of our Fathers is playing at Trafalgar Studios until 4 October. For more information and tickets see the ATG tickets website.