CHARLOTTE Jones’s astonishing first play Airswimming was inspired by a newspaper cutting announcing the “release” of perfectly sane women from decades of incarceration in hospitals for the mentally ill, better known at the time as lunatic asylums. The 1913 Mental Deficiency Act enabled angry, disappointed and embarrassed families to categorise their errant daughters as “moral imbeciles” and, with a doctor’s signature, consign them to a life locked away from society.

Many of these women had borne illegitimate children. Some were “a bit different”, not conforming to familial expectations. The Community Care Act of 1990 released most of the remaining inmates into the community and closed many large psychiatric hospitals.

The playwright, who has gone on to great success as a TV scriptwriter and with works like Humble Boy, saw the cutting and created a backstory for Dora Kitson and Persephone Baker, who spent more than four decades in an asylum for the criminally insane. During that time the two oddly-matched women forged a dependent friendship and created alter egos, Dorph and Porph, in whose identities they managed to prevail against their hideous fates. The title comes from the only sort of swimming that was available to them. Porph was obsessed by Doris Day, with every song, every speech and every nuance committed to memory and trotted out to raise the mood, every day. Her father had her locked away because she had a baby by one of his married friends. Dorph, whose three brothers were killed in the Great War, revelled in a military bearing and tales of derring-do, plotting an (impossible) escape over the years of imprisonment.

It is impossible to stage this powerful, sometimes funny, angry and human play without two exceptional actresses, and the Swan has them in Sarah Nias and Jo Simpson. Directed by Sarah Ambrose, herself a well known and versatile Swan actress, with a grimy institutional set created by Sian Spencer, this is a once-seen-never-forgotten play. The changes of tempo and mood propel the action and the two women capture the fluctuating affections, dependencies and love to perfection, on a minimal set with perfect little period details.

It’s a hard watch … impossible not to share in the womens’ uncomprehending frustrations and wonder at their extraordinary powers of endurance – impossible not to be appalled by the fact that it only happened in the so-recent past.

Airswimming is another triumphant production at the Swan, where theatre-lovers can confidently go without thinking about the perennial amateur/professional questions. Jo Simpson and Sarah Nias are stupendous.

GP-W