Prom 17: Britten's Curlew River, Royal Albert Hall, London

There was a heavy police presence at this late-night Prom. Officers were patrolling the Albert Hall as we entered; a growing number of them were stationed at every entrance and exit. Now, you might expect crowd-control for a rock event, but a church parable? Well, that, as it turned out, was the first surprise that the director Graham Vick and his Birmingham Opera group sprang on us with this, their London debut. The last would come little more than an hour later, by which time every member of the audience - and some more than others - had been touched by, and played their part in, a quite extraordinary Prom event.

There was a heavy police presence at this late-night Prom. Officers were patrolling the Albert Hall as we entered; a growing number of them were stationed at every entrance and exit. Now, you might expect crowd-control for a rock event, but a church parable? Well, that, as it turned out, was the first surprise that the director Graham Vick and his Birmingham Opera group sprang on us with this, their London debut. The last would come little more than an hour later, by which time every member of the audience - and some more than others - had been touched by, and played their part in, a quite extraordinary Prom event.

Benjamin Britten's Curlew River - a dramatic fusion of East and West, Japanese Noh play and English mystery, sacred and secular, ritual and narrative - is about redemption for the departed and closure for the living; it's about communal response to death and despair; it's about grieving; it's about us. By conceiving the piece for church performance, Britten overlaid his own Christian ethics on the drama.

Vick and his superb ensemble turned that on its head. The Christianity here came at a price. Not so much care as fear in the community. By presenting Britten's abbot and monks as law enforcement, Vick questioned the whole concept of organised religion. One strict order was supplanted by another. The message: "You will believe."

These "authority" figures told us, quite literally, how to think, how to react, where to move. They, in every sense, manipulated us, their audience, even serving as marshals to clear space for the actors in the central acting arena. It's one of the abiding characteristics of the Birmingham Opera Company that it seeks to move among its community, to inhabit spaces and involve its audiences in ways that most companies would not contemplate. It says much for its performing skills that it so successfully shrunk the Albert Hall space without in any way diminishing the venue's impact or our involvement.

At the heart of the action, sunk into the central dais, were the instrumentalists, the Birmingham Contemporary Music Group, eloquently pointing up the resourcefulness of Britten's instrumental haiku. This, an exquisite fusion of distinctive East-West sonorities, combined the ecclesiastical (wheezing chamber organ) and the ethnic (drums, flute, twanging harp). The principal performers - Mark Wilde as the Madwoman, Rodney Clarke as the Ferryman, Iain Paterson as the Traveller - moved among us on floating rostra, the Ferryman steering his craft through a human sea.

The Madwoman's search for her lost child, for some kind of closure to her inconsolable grief, was movingly enacted by Wilde with his/her empty pram, the peculiarly distracted oscillations of the vocal line echoed in a kind of shadow play by the flute. When the community discover the child's fate, they recast "the Madwoman" as "the grieving mother". Suddenly, she is the centre of media attention - photographers, camera crews, doting law enforcement. Her son's tomb is a box of personal effects - the remaining "evidence" of his life.

In the final moments of the performance, as we hear the voice of the boy (Benjamin Durrant) wafting magically from afar, a section of the audience suddenly reveal its "evidence" - toys, garments, souvenirs of lost childhoods. And, while the authority figures congratulate one another on a satisfactory conclusion, we weep.

Proms end 11 September. Prom 17 available online until Wednesday (020-7589 8212; www.bbc.co.uk/proms)