The UK’s first reggae band deserves all the love and attention coming their way with the release of this documentary. It’s the untold story of Cimarons, and begins in 1967 at a bus stop in London’s Harlesden where two Jamaican-born Londoners, Locksley Gichie and Franklyn Dunn, met and formed a band. By the end of the decade Cimarons would become the go-to backing group for Jamaican artists touring the UK, playing with the likes of Jimmy Cliff and Bob Marley. The band recorded albums of their own, worked as session musicians for Trojan records and toured with the Clash and the Jam. “They were the spark that started a big flame” is how MC General Levy describes their influence. But they barely made a penny out of music. Today, the band’s singer Michael Arkk works as an officer cleaner. How did Cimarons become reggae’s forgotten heroes?

Partly it comes down to choices. The band never hired professional management. They were in it for the music, touring in a clapped-out van with no heating and broken windscreen wipers. They called themselves Cimarons after a TV western, and only later found out it meant “wild and free”. The name fits.

And then there was the music industry. Record labels were intimidated by how to market Cimarons; their sound was too raw. An NME article from 1976 reports that the BBC was refusing to play reggae, claiming there was no audience. If Cimarons had been a white band or a rock band, their journey would have been different, says another talking head. Film-maker Mark Warmington tells the story diligently and follows the band’s first gig in 30 years. Which feels like too little, and sadly is too late for one member, but it’s heartwarming all the same.

• Harder Than the Rock is in UK cinemas from 3 October.