Jeff Bridges played Bad Blake, a drunk, self-destructive country singer in Scott Cooper’s passable 2009 film Crazy Heart. Bad Blake charmed the women, and one woman in particular - Maggie Gyllenhaal’s music journalist - despite everything. But Blake was too good to be true; heck, he was lovable. That was the sanitised, feel-good version.

Irish director Paul Duane's documentary Very Extremely Dangerous, on the other hand, is the real deal: the reality of being an utterly screwed-up musician, hell-bent on destruction, pointlessly trying to make a comeback. Quite aside from the drugs he is taking for diabetes and other ailments, Jerry McGill is addicted to any drug he can get his hands on, including dog tranquilisers.

He is reliant on the charity of extraordinarily tolerant friends, who must know a side to him that is not predatory and selfish, or prone to violent outbursts. There is a fiancée called Joyce, who will not let the camera show her face. She and McGill have hooked up again after a 40-year hiatus, thanks to the internet. If Joyce did allow the camera, we would see the tormented features of a medieval martyr.

Jerry McGill was seriously ill with lung cancer, and aged 70, when Duane began filming in 2009, his glory days, for what they were, well behind him. An early video from the mid-Seventies shows him singing a funky thing called Hoochie Coochie Man (not the Muddy Waters blues standard). The man exudes Jagger classiness, John Hiatt swagger, a raspy Southern musical accent to the song. McGill wrote numbers that were covered by Waylon Jennings, BJ Thomas and David Allan Coe, but the early promise of his single Lovestruck (released on Sun Records) was dissipated in drugs, guns and knives. That and time spent running from the law, or in prison - nine years in total imprisonment, one of his three-year terms spent under an alias.

We see McGill make some kind of ragged comeback in a Memphis club, with a washboard-playing friend. He sings a sentimental song or two that Charlie Landsborough would be happy to cover. The poor man’s voice is completely shot; he plays one of those nylon-stringed guitars and the chords sometimes don’t seem right for what he’s singing.

There is something to be said for giving a man a break at the end of a hard, vagabond life, but people generally only want professionalism when they pays their money. I'd much prefer to see a film about real long-stay country talents like Guy Clark or Rodney Crowell - and so what if the resultant film was less lurid and sensational? McGill’s comeback was never going to be more than a token one. Does his life merit a film then? That’s a moot point. Can be seen exclusively at the IFI, Dublin.

Paddy Kehoe