In 1969, six years before Comedians brought him international acclaim, Trevor Griffiths wrote this one act black comedy, which sat gathering dust in a filing cabinet for over 30 years before it was published by his wife in a recent anthology of his plays.

Set in a public toilet, it centres on Alfred Rimbaud Thin, a white collar worker who finds himself accosted by two violent and shady 'detectives'. Telling him he's being questioned in relation to a murder case (the dead body happens to be in one of the cubicles), they proceed to press this ordinary man into laying bare his private life, most notably the fact that he's gay.

Written in the wake of the 1967 Sexual Offences Act, which decriminalised homosexuality, it ruminates on the issue of sexual privacy, and feels remarkably contemporary in its humour and tone.

Like Goldberg and McCann in The Birthday Party, the identity of the inquisitors  (known simply as Number One and Number Two) remains shrouded in mystery. But, as with Pinter, it doesn't matter who they are – the point is who, or what, they represent.

As the perpetually terrified Thin, Richard Sandells finds just the right balance of meekness and inner strength. Despite disclosures of some deeply disturbing secrets, including an incestuous liaison, he emerges as a likeable everyman, a dignified fossil in the ongoing erosion of privacy rights.

As his interrogators, Ryan Gage (One) and Alan Francis (Two) make a fine double-act, with Francis particularly strong as a dour Scottish stooge. “You can't defend democracy with kid gloves” he snarls in defence of his violent approach, one of the countless sharp one-liners peppering the dialogue.

This is a gem of a play, and full credit to director Prasanna Puwanarajah and his company for unearthing it. Deftly realised on designer James Cotterill's impressively rendered public convenience, it provides a fascinating insight into the early workings of one of our finest contemporary theatre minds.