In the mid-Eighties four huge rock groups – Bon Jovi, The Scorpions, White Snake and Anvil – headlined festivals together around the world. While the first three bands had blazing careers, Anvil disappeared swiftly into obscurity.

Twenty years on, former fan and documentary-maker Sacha Gervasi Googled Anvil to discover they'd never stopped performing. After contacting lead singer Steve "Lips" Kudlow and drummer Robb Reiner, Gervasi travelled to Canada to make a film about the band.

Anvil! The Story of Anvil is a wonderful, warm, moving film that speculates on our capacity for perseverance in the face of failure. “The music lasts forever,” says Kudlow, then adds “Maybe the debt does too”.

Beautifully shot, the film crackles with excitement and humour. There are shades of Metallica’s revealing backstage documentary Some Kind of Monster, and conscious parallels with This Is Spinal Tap, but the film owes little else to anyone except Anvil themselves.

The relationship between band members Kudlow and Reiner is compulsive viewing. Their dedication to one another, and to their art, is inspiring, poignant and hilarious. Despite their lack of commercial success, Anvil have long inspired passionate support from luminaries of the genre such as Metallica drummer Lars Ulrich and Slash from Guns N’ Roses. Fanboy Keanu Reeves introduced the London Film Festival screening.

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