“Hard stop” refers to a “controversial” practice whereby unmarked police cars kettle and bring a suspicious vehicle to a halt, without any warning.

That is what London’s Metropolitan Police were doing when they accosted and killed Mark Duggan, a 29-year old father of six from Tottenham. Duggan’s death would spark the London riots of 2011, an unrest that quickly spread to towns and cities in England including Birmingham, Coventry, Leicester, Derby, Wolverhampton, Nottingham, Liverpool, and Manchester. Five people were killed and more than £200m of damage was done to property, nationwide.

And yet, improbably, after police pieced together CCTV footage, they blamed one man for starting the riots: Mark Duggan’s friend, Marcus Knox-Hooke.

George Amponsah’s moving, clear-headed documentary follows Knox-Hooke and another friend, Kurtis Heville, long after the news cameras have departed. Both men are seeking justice for their friend and, to this end, frequently come together with Mark’s mother, wife, children and various community leaders. Both men, equally, are seeking better lives for themselves.

The lively Kurtis spends much of the film job-hunting. It’s not easy and when he finally lands a gig in Norwich, the lengthy commute causes friction with his partner and family.

Knox-Hooke, meanwhile, must serve time for actions committed during the riots. He emerges determined to keep Mark Duggan’s young son - who touchingly spends much of his time listening to his dad’s rap demos - out of trouble.

The Hard Stop doesn't spoon-feed its audience. The film prefers driving around Tottenham's Broadwater Farm with the two riled, but grief-stricken men listening to stories from their childhood and teens. Composer Roger Goula Sarda provides the melancholic score.

The economically deprived, racially diverse borough where Knox-Hooke, Duggan and Heville grew up, was made famous by the death of a police officer during earlier riots in 1985; those riots were also sparked by heavy-handed policing. That death inspired more heavy-handed tactics. And so on.

More than 30 years on - and five years after the death of Mark Duggan - this is an emergency situation. The film, accordingly, ends with a chilling statistic: despite approximately 1,500 UK deaths following contact with the police since 1990, not a single officer has been charged in any of these cases.