Illegal bare-knuckle fights are still held in non-sporting venus like underground car parks in London or - as the new documentary film Knuckle demonstrates - on the edge of Traveller encampments all over the UK.

Directed by Ian Palmer, who began the project by filming the wedding of Michael Quinn McDonagh until his introduction to this hidden world took over, Knuckle explores the world of bare-knuckle fighting, and for 12 years it has tracked the longstanding feud between the three Irish Traveller families, the Quinn McDonaghs and their opponents the Joyces and the Nevins.

The grudge between the families began after two different Traveller clan members had a fight outside a London pub in 1998, which ended in the death of one and a manslaughter conviction for the other.

Read more:

Irishman charged with inciting hatred of Travellers on Facebook

‘Big Fat Gypsy Wedding’ Irish Travelers plan to sue after TV show - SEE PHOTOS

‘My Big Fat Gypsy Wedding’ an insult to Irish travelers - SEE PHOTOS & POLL

Palmer's cameras follow James Quinn McDonagh, who after years of remaining unbeaten, freely admits he's grown tired of all the fighting.  Enter his more confrontational younger brother Michael, who hopes to retrieve the honor he feels he lost in an unfortunate bout nine years before .

The bouts themselves are shockingly violent. In between the bouts, we see the homemade videos that the clans send to each other as provocations, while various sociologists provide some insight into the psyche of the male Traveller.

Knuckle asks some hard questions about the feud that seems to be all these communities live for, but its impossible to look away. 'At least wars are about something!' says one onlooker in the film. And that may be why they endure.

Knuckle is on general release in UK cinemas from 5th August.

Documentary examines the brutal world of bare ‘Knuckle’ fighting