The Veteran (2011) on Netflix

Plot summary

The Heygate Estate in South London is a decaying neighborhood overrun by gun-carrying youth gangs led by the drug lord Jones, and it is where paratrooper Robert Miller comes home from the war in Afghanistan. Jones offers Miller a job; Miller turns him down. Through an ex-army friend, Miller finds work in undercover surveillance. Two government operatives then recruit him for an operation watching a network of people suspected of belonging to terrorist cells, and a Lebanese-born British informant is embedded inside that network. Miller, unable to settle back into civilian life, sets his mind on bringing down the gangsters in his neighborhood.