In new play After Party, Ben Keyworth presents a blackly hilarious vision of chemically-fuelled claustrophobia that feels like a clubber’s riposte to No Exit, the Sartre play that made famous the line: ‘Hell is other people’.

After a big night out to celebrate her younger sister Lena’s 25th birthday, Laura and her boyfriend Joe are back at their flat, drinking tea and fretting about getting too old for it all when two of Lena’s friends arrive at the door, bug-eyed and sweaty and intent on getting more so. Lena’s nowhere to be seen, much to Laura’s consternation, but when she does arrive, a pair of dodgy-looking geezers in tow, one can’t help wishing she’d stayed out. The evening starts becoming as unpredictable as the pills as tensions bubble and the guests drink, flirt, fight and vomit in a hedonists’ purgatory.

Keyworth’s writing rings uncomfortably true, from the competitive nostalgia for decent ecstasy to the tedious proclamations that someone’s "a beautiful person, y’know, inside and out." And it’s very, very funny; witness Tomi May, perfectly cast as thuggish, volatile Leon, unleashing a tirade of expletives on gnarly old raver Davis then flipping to Hyacinth Bucket when his friend dares to talk back, with a scandalised: “We are guests here!”

The cast hits the script full throttle; Madeleine Herrington is spot-on as Lena, veering queasily between self-indulgence and self-loathing, Jen Bridges’ Laura hovering nervously behind her with the spectre of Parties Past laid heavy on her mind. Leon is given depth and an ugly humanity, while Katie Cooper and Matthew Lawson as guileless Fran and her idiotic boyfriend Fergus are comic gold. The show was dealt a late blow by the loss of actor Phil Kavanagh, who had been injured earlier in the evening, but director Nick Warnford stepped up to the role of Joe admirably.

This isn’t a perfect production; the ending is drawn out further than it needs to be and the tension built up in the first half has to be recreated almost from scratch by a badly timed interval. But whether closely acquainted with such early-hours nightmares or blissfully ignorant of them, this is an impressive, ambitious slice of theatre that shines a light on the dark underbelly of partying.