- Directors: Daniel Barber
- Producers: Matthew Vaughn, Kris Thykier, Matthew Brown, Keith Bell
- Writers: Gary Young
- Genres: Thriller
- Actors: Michael Caine, Emily Mortimer, Ben Drew, Charlie Creed Miles, David Bradley, Jack O Connell, and Liam Cunningham
The film opens with the gang initiation of a boy on a council estate in South London, and in a scene apparently filmed on a mobile phone, three gang members harass and shoot dead a mother walking her child. While attempting to escape by motorcycle, they speed across a road in front of an oncoming truck and are also killed. The titular Harry Brown (Caine), an elderly former Royal Marine suffering from emphysema, wakes to news of these deaths over the radio. With his wife sick in hospital, in order to visit her Harry must cut through a public underpass which is a gathering spot at all hours by local chavs and gang members.
Though seeing the increasingly brutal facts of life on the estate (including a man beaten for attempting to intervene when his car is broken into by a gang of youths) Harry is unwilling to get involved. In fact, it seems Harry’s only real friend is Leonard (Bradley), another pensioner who complains that hooligans put dog faeces through his letterbox and spit on him. The pair play chess at a pub run by Sid (Cunningham), who takes kickbacks from a pair of drug and arms dealers, something Leonard cannot forgive but which Harry is willing to ignore. That night Harry is informed that his wife is dying, and he attempts to get to the hospital before she expires; however, in order to do so he must go through the underpass, something he is unwilling to do. By the time he finds an alternative route to the hospital his wife is already dead. After the funeral, Leonard confides that he can no longer take the insults and indignities the youths foist upon him and he shows Harry a First World War bayonet he has taken to carrying in his jacket. When Harry tells him he should put the knife away and talk to the police, Leonard admits he has done so but they ignored him. That night Leonard wakes in his flat to find someone has put burning dog faeces through his letterbox.
At a conference held after the riot, SI Childs explains that DS Hicock would be given a posthumous commendation and that the actions of the police helped lower crime on the estate, refuting claims that a “vigilante” had anything to do with it. The final scene is of Harry Brown walking toward the underpass, which is now silent and safe compared to the beginning of the film.