The Willard Grant Conspiracy, Union Chapel, London

It shows where rock'n'roll's come to, and from, that this beautiful old north London church now seems a natural place to hear music once despised as sacrilegious. The reading of parish notices about church roof repairs before Willard Grant Conspiracy appear shows this is a more polite, English setting than the holy rolling Southern churches rock was partly born from. But as we settle in hard wooden pews, and singer Robert Fisher stands in front of a pulpit with his band arrayed in the shadows, the night prepares for a kind of testifying.

Willard Grant Conspiracy's music has always been about confession and community, to which their fifth album, Regard the End adds an obsession with death, and living in its shadow. What makes this chapel such a fitting setting for them, though, is Fisher himself. A big man in black, with a white-streaked beard, he stands at first, hands in pockets, letting his grand, deep voice leave his body casually. The church's acoustics amplify every note, like a sacred Sun Studios, channelling his words as they would any prayer.

But it's when he sits for "The Monster Inside", about his alcoholic past and its wretched cost, that the full power of this band and man explodes. Fisher's voice, till now stately, suddenly roars from almost nothing, like a hurricane in a clear blue sky. The band shake, sway and saw their instruments, swept up. The force of Fisher's scarily huge voice in this echoing chamber builds with no way of escape, till it seems something must smash. The fearsome emotions that Fisher once owned make him close his eyes - the still, suffering centre of his song's wild storm. When it has blown out, the cheers are enormous.

There's a gap while Fisher, wrung out, collects himself, time enough to think how much like Jim Morrison (minus the bombast) he sounds. When the Conspiracy follow with his classic, minor key piano ballad of inner desolation, "Massachusetts", it makes me wonder just what has stopped them being recognised as one of the great American bands, with a classically accessible songbook and controlled musical power matching any contemporaries.

Though nothing that follows matches the central brace, other highlights abound: the tense, traditional blues "Another Man Is Gone", in which Fisher slowly moves his head from his mic so that his howl fades as if falling down a mountain; the Conspiracy's free yet focused rock, bluegrass and folk interaction throughout; and the night's final notes, an a cappella verse finally reduced to Fisher alone, sustaining notes almost showily. Among the pews, more converts have been made.