You’ve probably never heard of Anvil, but bands like Slayer, Metallica and Anthrax all cite them as an influence. Formed by childhood friends Steve ‘Lips’ Kudlow (on vocals and guitar) and drummer Robb Reiner in 1973, they tasted success in the 80s with the release of Metal on Metal (featuring the classic chugging title track). Director Sacha Gervasi was a huge fan: ‘I was obsessed with heavy metal and especially Anvil, I saw them playing the Marquee and the show was unbelievable. Lips came out playing the guitar with a dildo and the music was heavy as fuck.’ Gervasi even roadied for the band on a UK tour at the age of 16. Then, intrigued as to how his favourite band were faring, a quick search on the internet revealed they were still plugging away.

The result is one of the greatest music documentaries of all time, which follows Anvil on a ramshackle European tour where tempers fray, trains are missed and crowds are thin. ‘When you’re not a big selling commodity it’s just the truth of the situation,’ explains Kudlow, as honest and excitable in the flesh as he is on screen.

Of course comparisons with 1984’s This is Spinal Tap are inevitable ‘If you make a documentary about a rock band it’s always going to be compared to “the almighty”,’ explains Kudlow. ‘Spinal Tap is so good because it copies reality, but this is real.’ And while there are plenty of laughs, the real heart of the film is the bond between Kudlow and Reiner and their undying commitment to their art. ‘No one’s expecting that a movie about a “silly” heavy metal band will become a heartfelt story about perseverance, friendship and family,’ adds Gervasi. ‘It was very personal, I saw the movie three times, immediately, bang, bang, bang,’ adds the stoic Reiner, ‘but we’re still brothers and we’re still rockers.’

The film hasn’t even opened and already momentum is building. There’s an online petition to get Anvil to open Glastonbury, they are now working with Slayer’s manager and Coldplay’s booker. ‘We’re coming into the summer of our career, it’s been a long, long winter but the sun’s gonna come out,’ says Kudlow. ‘This is the Rocky Balboa of heavy metal, people want to see us win the fight, I’ve been punching sides of beef for 30 years. The most important point is the ending of the movie is not the end, we’re writing that now.’

Anvil – The Story of Anvil is on selected release from Fri 20 Feb.