Sean O'Callaghan (Phil) and Janet Etuk (Grace)
Sean O'Callaghan (Phil) and Janet Etuk (Grace)
© Mark Douet

Misery and indignity can make for compelling theatre, especially when presented with scrubbed, raw naturalism, in real time, with silence and snippets of dialogue, and the rhythm of work, seriously underpaid work, beating like a pulse in the background.

Alexander Zeldin devised and directed this play about zero-hours contract cleaners in a meat factory with five actors at the Yard Theatre last summer, and it's absolutely right of the National to bring it to wider attention in the Temporary Theatre (the former Shed, still awaiting a new baptism).

One of those actors has been replaced, but there's a palpable sense of something deeply felt and deeply desperate going on here, as the lives of the three women from an agency – Grace (Janet Etuk), Susan (Kristin Hutchinson) and Becky (Victoria Moseley) – filter through their quietly stated, confidential scenes with each other, the equally miserable male cleaner Phil (Sean O'Callaghan) and the bullying supervisor on the floor, Ian (Luke Clarke).

This is taking the "work" plays of David Storey, Arnold Wesker and Richard Bean through a more obsessively Mike Leigh process of observation and (I would imagine) research, and into a bleak new dimension of working lives at rock bottom.

The repressed tone is set by the demands of ID's for this form of slave, risibly paid, labour, sudden lurches into extra hours when a new sausage with thyme line is being launched, patronising remarks about the staff party being a great opportunity for cleaners to meet the "normal" staff and one absolutely relentless, unwatchable episode of rough, unpleasant sex on the factory floor.

But even this has a warped lyricism about it, the participants being Becky and the supervisor, who's 50 years old. Becky is borderline psychotic, with a child she can't see; Susan very possibly homeless, but unable to admit this to anyone; Grace, the oldest, struggling to cope with rheumatoid arthritis. None of them can afford not to say no to working through the night. And adding insult to injury, the coffee machine keeps swallowing their loose change.

The atmosphere is superbly maintained not just by the high level of acting, but also by the design of Natasha Jenkins (obviously authentic meat factory equipment), lighting of Marc Williams and sound of Josh Grigg. This is the first project by Zeldin and his students from East 15, where he was a guest tutor, and it's so impressive and powerful a start you just wonder if they might not form a creative mini-nucleus within Rufus Norris's new National.

Beyond Caring runs at the NT Temporary Theatre until 16 May.