What a touching, unique show this was. And what a pity that, after three performances, it seems likely to disappear into the mists of memory. Even on paper a collaboration between Streetwise Opera and the Shout looked intriguing. The former works with 600 homeless people a year – literally giving them a voice in stage productions and workshops. The latter is a versatile choir of professional singers from all sorts of music and theatre backgrounds. But their combined effort, Critical Mass – a 75-minute concoction of speech, movement and folksongs from many lands – far exceeded expectation, just as it defied categorisation.

In part, it was political satire. One by one the singers, dressed as business types and seated in rows, jumped up to spout real-life political platitudes, ranging from chilling Oswald Mosley speeches to reams of nonsensical Blairite jargonese. These were intercut with folksongs – many recalled by the performers, drawing on their own ethnic backgrounds. The intensity, spontaneity and rough authenticity of the latter offered a telling contrast with the hollow insincerity and empty promises of the politicians’ rhetoric.

But the show was also a powerful plea for the acceptance of loners and outsiders, of individual conscience, and of the differences between us, in a world that increasingly demands conformity. Halfway through, a woman who had been rebelling quietly against the barrage of political claptrap suddenly falls dead – as if this supreme sacrifice was the only protest left to her. Then someone else did, and another. From that point on (the show seemed to be saying) there were enough people willing to assert their individuality to form a “critical mass”, and so challenge the status quo.

That’s how I saw it, anyhow. But Critical Mass was open-ended, and enjoyable on many levels. The choral arrangements, for example, had a magical, loose-limbed feel, as if improvised on the spot – though they were performed with wonderful energy and assurance. They were devised by Orlando Gough, who also supplied a hilariously maze-like round based on Donald Rumsfeld’s notorious “known unknowns” speech. Emma Bernard’s direction, too, made resourceful use of the cast’s necessarily diverse talents. There wasn’t a whiff of condescension: just a surreal sense of some blissful world having been created in which all people can fulfil their potential – if only for an hour or so.

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