At the Sundance Film Festival last year the film received a rapturous welcome. Art-house cinemas picked it up for distribution in the UK and US earlier this year, which brought it to the attention of more rapt critics. "The first great film of 2009" - NME. "A hell of a movie" - Empire. "The best documentary I've seen in years!" - Michael Moore. Even the New Yorker's normally hard to please Anthony Lane found it the "most stirring release of the year".
So much for Anvil! the film. But something even more extraordinary has been happening to Anvil the band. I catch up with Lips on the phone on his way to a gig in San Francisco. It is a gig with a difference: the band is performing in a cinema directly after the end of the screening in what is being billed across several US cities as the "Anvil Experience".
When they did the Anvil Experience in Los Angeles recently, Lips was amazed to see Dustin Hoffman standing on his seat doing devil horns and singing along to Metal On Metal. Fan mail has been pouring in from thousands of Americans saying that the band's dogged determination has inspired them.
"I've been getting confessional letters from people from all walks of life who can barely make their mortgage payments saying if you guys can keep going anything is possible."
The 13th album has been selling like hot cakes through Anvil's website, and Lips has all but paid his sister back. Now they are on to the 14th - working title Juggernaut of Justice. Even Keanu Reeves, whose glasses Lips failed to sell, has gone on record saying: "I bow at the feet of Anvil."
Maybe there's a lesson in this. I wonder if the Roll Ons would be up for a reunion.