Kings of Leon, Hyde Park

Brothers Caleb, Nathan and Jared Followill and their cousin Matthew Followill, better known as Kings of Leon, have come a long, long way from their humble Tennessee roots in the last 12 years. In London last night playing to a 65,000-strong crowd in the same week that a documentary charting their rise hits cinemas, the contrast between the life they were born into and the one they have carved out couldn’t be more marked.

Opening with the Aha Shake Heartbreak hit "Four Kicks", people screamed and danced about to the roaring of electric guitars and the growling twang of Caleb’s voice. But judging from Talihina Sky: The Story of Kings of Leon, the aforementioned feature film made by Stephen C Mitchell, you might expect this quartet to have turned out more Jonas Brothers than prog-rock ingénues, charting as it does their strict Pentecostal upbringing, impoverished living conditions and tense relationships with religion and music.

Caleb, who harboured dreams to become a preacher, repeatedly thanked God for letting them be Kings of Leon

There’s a sequence in the film where footage of the Followills speaking in tongues in church as young boys is interspersed with images of them performing as Kings of Leon. Watching them rocket through "The Open Road", "Molly’s Chambers" and "The End", you can find something rapturous about their eyes-closed performance style. Caleb, who the film reveals harboured dreams to become a preacher, repeatedly thanked God for letting them be Kings of Leon, his gold crucifix visible against a green T-shirt – the devout words only undermined somewhat by his calls for more drinks.

Everybody clapped vigorously to "On Call", only wearying slightly during an overlong guitar solo. It was followed by the appropriately country-influenced "Back Down South" – a tender nod to their Tennessee and Oklahoma heritage and the bluegrass sounds their grandfather Leon (whom they named the band after) passed on to them.

Another golden oldie, the gutsy guitar of "The Bucket", got people mouthing along and jigging about. Standing in Hyde Park surrounded by people who’d slung wellies over their work clothes, I found it a rather surreal festival atmosphere. The queues to the portable loos and the swirl of churned mud at our feet made it easy to forget that offices and homes were less than a stone’s throw away.

The rain threatened to return briefly as the sun began setting late on this midsummer evening, the whoops of "California Waiting" offset by a dramatic pink sky. Caleb apologised for “sounding like a frog” – his husky style evidently having taken its toll on his throat - but his note-perfect precision was unaffected. Finishing with "Sex on Fire" before returning for three encores, they whipped the crowd into a frenzy, singing along, arms waving, lungs bursting.

The telling of the truly extraordinary story of their success via the documentary, not to mention their struggle to reconcile rock‘n’roll with God, might damage the mystery for some fans. But as a snapshot of the environment in which their prodigious talent was fostered - albeit one which tried to squash the “devil music” out of them - it is as compelling as their live performance.

• Talihina Sky: The Story of Kings of Leon hits cinemas nationwide on 25 June
• Find Kings of Leon on Facebook
• Find Kings of Leon on Amazon