The film opens with Harry Mitchel (Colin Farrell) (convicted of grievous bodily harm under never-explained circumstances) leaving prison. He is propositioned by his friend and former partner-in-crime, Billy Norton (Ben Chaplin), to live in a nice "acquired" apartment, but on condition he work for Billy's criminal boss. On his way to a "welcome back" party, Mitchel saves a woman, Penny (Ophelia Lovibond), from being mugged. At the party, Billy propositions Mitchel again. Mitchel is told by Billy and their contact, Danny (Stephen Graham), that his sister, Briony (Anna Friel), is in the basement, and he "saves" her from being raped by a drug addict. Mitchel meets Penny for a drink elsewhere, and she offers him a job to help her friend, a reclusive famous "retired" young actress, Charlotte.
Mitchel goes to a train station to visit his friend Joe, a blind homeless Big Issue salesman and gives him a knife to protect himself. The next day, Mitchel meets Charlotte (Keira Knightley) and her friend, Jordan (David Thewlis). Charlotte is constantly hounded by the paparazzi perpetually stationed outside her home, taunting and photographing anyone who enters or leaves. Mitchel is offered the job to "assist" and Jordan gives him a tour of the mansion, including a collection of paintings that look like Francis Bacon's studies on Velazquez screaming Popes and a garage full of Charlotte's ex-husband Tim's cars. At his apartment, corrupt police Detective Bailey (Eddie Marsan) visits Mitchel and tells him to avoid Billy and forces a small bribe from Mitchel.
Mitchel talks to Billy about Detective Bailey, whom Billy cannot stand. Joe is mugged, then brutally beaten by two 16-year-old footballers from the estate and left for dead; and one of the boys takes Joe's knife. At the hospital, Dr Sanji Raju (Sanjeev Bhaskar) lets Mitchel visit Joe, who wants Mitchel to avenge his death. The next day, Billy tells Mitchel that he knows about the car collection and that his boss wants to steal them. At Joe's funeral, Dr Raju tells Mitchel that he wants to date Briony, which Mitchel accepts. Mitchel goes to the pub and asks Danny to find out as much as he can about the two footballers. That night, Mitchel is kidnapped by Billy and taken to his boss, Rob Gant (Ray Winstone), who insists that Mitchel collect money for him.
Charlotte and Mitchel escape from the paparazzi to her mansion in the countryside. Charlotte mentions to Mitchel that something happened to her in Italy, which is implied to be a drug overdose. Jordan reveals to Mitchel that in this incident she was raped by a drug addict, who never got caught but is currently on life support after overdosing on quaaludes, administered by Jordan.
Gant threatens Detective Bailey to stop him making Mitchel pay bribes. Later that evening, Mitchel and Billy meet Gant in a garage, where Gant shoots a black man, whom Gant was led to believe by Billy to be one of the Nation of Islam members who beat up Mitchel and scared off Billy while earlier collecting for Gant. Gant yells at Billy, but Mitchel protects Billy and yells at Gant, who claims Mitchel said to kill anyone. Gant tells Mitchel he is now an 'accessory' to the killing, and to meet him at Criterion Restaurant the next night, for an unknown arrangement.
Charlotte tells Mitchel she loves him. Later, Mitchel and Gant meet and Gant assigns Mitchel to collect money in Streatham, Clapham and Kennington. Gant reveals that the main mugger-footballer has a future and is being scouted by professional teams, and implies that Mitchel had best leave him alone. Mitchel tells Gant that if he were a gangster, Gant would be the first person he would kill and would take everything Gant has, but claims he is not a gangster and walks away. Gant, to put Mitchel in trouble, waylays the doctor who owns Mitchel's apartment and after Gant rapes him, he orders his henchmen, Fletcher (Matt King) and Beaumont (Nick Bartlett) to kill him. Mitchel learns who the footballer is and follows him into a tunnel, planning to shoot him, but has a change of heart at the last moment, and lets the young man walk away unaware.
Mitchel visits Charlotte and tells her that he loves her; the two sleep together. Mitchel sees Billy's van and attacks Billy, who says that Gant sent him to kill Mitchel; he warns Mitchel to look for "a big Bosnian fucker". Mitchel borrows one of Charlotte's husband's Rolls Royces and confronts Billy at a pub. He beats Billy, who says Gant will kill everyone whom Mitchel loves, and Mitchel steals the money Billy collected for Gant. Mitchel meets his sister at a restaurant in order to persuade her to get out of the country so that she is out of Gant's reach. He gives her a train ticket and money, but she belittles his worry and ignores the warning. Mitchel and Jordan find Billy's dead body in the front garden of Charlotte's home, and the Bosnian, named Storbor, standing outside the gate.
Mitchel asks Jordan to help him kill Storbor and the two follow Storbor to a nightclub where they meet him and the drug addict from the party named Whiteboy (Jamie Campbell Bower). In the final scenes of the film, the story is resolved as Mitchel and Gant each race to prevail over the other.Colin Farrell as Harry Mitchel, an ex-convict
Keira Knightley as Charlotte, a reclusive young actress
David Thewlis as Jordan, Charlotte's agoraphobic business manager, who soon befriends Mitchel and helps him out during the film.
Anna Friel as Briony Mitchel, Mitchel's "wild" sister who meets and later dates Dr Raju.
Ben Chaplin as Billy Norton, a none-too-smart criminal and friend of Mitchel's
Ray Winstone as Rob Gant, a crime boss and homosexual rapist
Velibor Topic as Storbor
Eddie Marsan as DS Bailey, a corrupt cop who is following Jordan and bribing Mitchel, causing him to get into trouble with Gant.
Sanjeev Bhaskar as Dr Sanji Raju, a friend of Mitchel's who begins to court Briony.
Stephen Graham as Danny, a contact of Mitchel
Ophelia Lovibond as Penny, Charlotte's friend
Simon Grover as the Porter at Storage.
Gerald Home as the Undertaker.
Matt King as Fletcher, one of Gant's henchmen.
The film is set in London, which is where the majority of the scenes were filmed, with some scenes shot at Ealing Studios. It was also filmed in Hammerwood Park, East Sussex. Filming began on 8 June. The giant billboard advertising posters of Charlotte's face that appear in the film were shot by fashion photographer David Bailey.
A trailer was released on 1 November 2010. The film opened in the UK on 26 November 2010.
IFC Films picked up the release rights in the United States and had a 5 October 2011 release date for the Video on Demand premiere, and an 11 November 2011 release date for the theatrical release.
The review aggregator Rotten Tomatoes reported that 33% of critics gave the film positive reviews, based on 39 reviews. The film has an average score of 52 based on 13 reviews on Metacritic.
Negative reviews tended to criticise the narrative as being unfocussed. The LA Times film critic, while praising the cinematography, a "beautifully bleak brush stroke of contemporary noir", and the "brutal extremes" of violence, wrote that "in trying to take a bite out of crime and another out of fame, [Monahan] ended up with more than he can chew for his first time in the director's chair". The NY Times review complained of "abbreviated, sometimes unnecessary subplots", and opined that "a few of the characters' cockney accents are so thick as to be virtually unintelligible." The A.V. Club review also complained of "a surplus of plot threads that don't have space to play out, and accordingly come across as clichés."
The film also received significant praise. Among positive reviews, Stephanie Zacharek of Movieline praised the cinematography of two time Oscar-winner Chris Menges, and the "aura of '60s stylishness", and noted that the violence is "deftly handled". In The Hollywood Reporter, Ray Bennett also praised the "gleaming cinematography of London at night", and the soundtrack that "succeeds in evoking the '60s while sounding entirely in the present." In The New York Post Kyle Smith wrote: "One of Hollywood’s most in-demand writers whips up a potent directorial debut with the vicious, spirited gangster drama 'London Boulevard'." The Urban Cinefile's review stated: "Fast paced with great cinematography and an upbeat score, this graphically violent thriller satisfies on every count".