Hailed by The Guardian as the greatest play of the 21st century (a bold claim in just 2009), Jez Butterworth's Jerusalem was an ambitious choice for Horse Box Theatre's latest offering at Quay Arts last week.

Directed by Ashleigh Mackness, this exploration of Englishness and modern life was a challenging three-hour staging, dominated by Mark Entwistle's mesmeric performance as the drug-dealing, forest-dwelling Johnny “Rooster” Byron.

From his entrance on stage, sticking his head into a bucket of cold water then downing a raw egg (yes, really) and vodka cocktail to ward off his hangover, Mark embodied Rooster with every fibre of his being.

So convincing was he, it was as though Horse Box had found him living in a caravan along the Undercliff and brought him to Newport to star in this show.

At times I felt a bit like I was actually eavesdropping on a bunch of low-life no-hopers, coming down from their latest all nighter in a forest clearing.

Parallels could be drawn between the underbelly of society in Wiltshire, as depicted in the play, and that of the Island. So striking, I would have been tempted to set Jerusalem on the IW, maybe replacing references to the Flintock Fair with Ventnor Carnival and Stonehenge with the Mottistone Longstone. Or would that be sacrilegious?

Threatened by the council with eviction from his illegally sited woodland caravan and the scourge of residents of the nearby estate with his drink and drug-fuelled parties, frequented by under-age kids, Rooster is a complex character.

He regales his entourage of deadbeat companions with tall tales, claiming Romany heritage back into the mists of time and kinship with English folkloric characters.

Darkly comic and simultaneously vulnerable and pathetic, Mark’s Rooster was the beating heart of this play.

His visceral performance was so utterly genius I found it difficult to believe he wasn’t actually like this in real life. He was terrific. I’d go to see any production he was in.

The supporting cast were equally authentic. It seems invidious to single anyone out as this was a true ensemble piece and all the actors were great, but for me Holly Downer playing coke-snorting mum Dawn, Ralph Hawtin as the aggressive Troy Whitworth, Omar Naguib as slaughterman Davey and Pete Stockman as pub landlord Wesley all deserve special praise.

Top marks also for the atmospheric set but in the audience, three hours on pretty uncomfortable seating was testing.