French director Jean-Stéphane Sauvaire adapts English addict and boxer William “Billy” Moore’s 2014 memoir about the three years he spent in Chiang Mai and Klong Prem, two of Thailand’s toughest prisons. A Prayer Before Dawn borrows its name from the book, though the source material’s subtitle, A Nightmare in Thailand, would be more fitting.

Joe Cole (Peaky Blinders) is a bubbling volcano of unexpressed emotion as Moore, arrested, presumably, for possession of drugs while on holiday in Thailand. The film isn’t interested in detailing his backstory. Instead, it seizes the moment of his arrest and zeroes in on the dizzying assault of suffering that follows. Sauvaire’s film is unblinkingly, exhaustingly violent, the ordeals on show grimy with blood, sweat, shit, piss, vomit and semen. Men are tortured over loudspeakers, gang-raped, pummelled within an inch of their lives for a hit of ya ba, a highly addictive form of crystal meth. The prison’s boxing team is Moore’s only solace; when he enters the ring for his final fight, it’s wearing a bamboo halo (or Jesus’s crown of thorns).

The combination of handheld HD cameras at close range and Nassim El Mounabbih’s astonishing sound design makes for primal, first-person cinema. The sensory thump of boxing gloves, of blood pounding in the eardrums, of flesh smacking flesh is interrupted by the woozy, disorienting silence of concentration while in the ring.

There’s little dialogue to begin with, but Sauvaire chooses to leave much of the film unsubtitled in a bid to further alienate the viewer, aligning them with Moore. At times this feels uncomfortable, the Thai characters at risk of reading as foreign savages. Yet many of the non-professional Thai actors, all ex-prisoners and real-life boxing champions, bring detail and lived experience to their performances.