A WHOLLY liberated production of Britten's Albert Herring - an opera about sexual liberation - has yet to be staged in Britain. Most versions of it are content to make do with ambiguity, which is what John Currie's did at the Perth Festival on Friday. A risque glimpse of the dishevelled Albert's unbuttoned fly at the end of the evening was about as far as it went towards uncovering the hero's covert homosexuality.

But Perth is Perth, and by the end of Act One some members of the audience had walked out on a work which, half a century after its Glyndebourne premiere, can still cause offence. In doing so, they showed their kinship with the forces of convention who, in the opera, are unable to accept Albert's emancipation.

Currie's production and his brisk, acid conducting of Britten's sharply satirical music, certainly underlined what Albert was up against. Though the precise nature of his sexuality was (as ever) concealed, the pomposity of his opponents was caught in vivid yet affectionate detail by a wonderful assembly of bigots, led by Rebecca Nash's unusually glamorous Lady Billows, supported by well-judged portrayals of the mayor, teacher, and vicar by Campbell Russell, Hilary Dolomore, and Alan Watt.

Mark Wilde's likeable but lightweight Albert, on the other hand, seemed a little too equivocal to be completely convincing.

But he rose stirringly to his final emancipation scene, which came as no anti-climax after a particularly moving account of the great choral threnody.

The fact that Herring turns on a knife-edge between comedy and tragedy was skilfully drawn, not least by Alison Barton as Albert's mum. James Paterson's sturdy, representational designs never impeded the action, which displayed Perth Festival Opera at its integrated best.

Further performances on Wednesday and Saturday.