In a thrilling twist of fate, four lifelong pals and minor London delinquents — Eddie, Tom, Soap, and Bacon — decide to combine their resources, amassing a whopping £100,000. They put their trust in Eddie's card-playing finesse as he steps into the high-stakes world of notorious gangster "Hatchet" Harry Lonsdale's coveted three-card brag games. Unfortunately, their inexperience soon turns against them, as they find themselves ensnared in a perilous situation where they owe Harry an extraordinary £500,000. With a harsh ultimatum hanging over their heads, they have only a week to settle the debt or face severe consequences. To complicate matters further, Harry aims to seize Eddie's father JD's bar as collateral, dispatching his menacing debt collector, Big Chris, to ensure payment is exacted from JD.
At the same time, Harry's greed drives him to pursue two rare and valuable antique Holland & Holland shotguns up for auction. Displaying his cunning nature, he recruits Barry "the Baptist," a seasoned operative who, in turn, hires the clumsy duo of Gary and Dean to snatch the prized weapons from a bankrupt nobleman. Unbeknownst to Harry, the bumbling pair mistakenly sells the shotguns to Nick "the Greek," a local fence, who remains blissfully ignorant of their true value. Consequently, Barry is left with no choice but to apply pressure on Gary and Dean to recover the stolen items.
Eddie's return home triggers a cascade of events that will change the course of his and his friends' lives forever. As he secretly listens to his neighbors — a ruthless gang led by the brutal "Dog" — plotting aheist against a group of cannabis growers loaded with cash, Eddie recognizes a golden opportunity. He shares his plan with Tom, Soap, and Bacon, and the four decide to strike while the iron is hot and target their neighbors after they've executed their heist.
The audacious operation executed by Dog's gang doesn't come without its hiccups, as they're met with casualties and unwanted attention from a traffic warden. Regardless, they manage to escape with a duffel bag bursting with cash and a van stocked with cannabis. Seizing the moment, Eddie and his friends ambush Dog's gang, taking possession of their vehicle and transferring the valuable loot to their own ride. To hide the evidence, they dispose of the traffic warden along the roadside and arrange for Nick to fence the cannabis to the notorious gangster, Rory Breaker.
Rory, initially pleased to purchase the drugs at a bargain, quickly turns furious when two of his men discover that they've been deceived, realizing that the very cannabis he just acquired has vanished. This prompts Rory to pressure Nick into revealing Eddie's whereabouts, deploying one of the growers, Winston, to pinpoint the culprits behind the heist.
As JD's crew celebrates at their favorite pub, Dog's gang, unknowingly aware of their friends' betrayal, sets a trap in Eddie's apartment. What follows is a chaotic encounter when Rory and his crew arrive, igniting a ferocious shootout that leaves everyone but Dog and Winston dead. Amidst the upheaval, Winston snatches the illicit goods, while Dog attempts to escape with the shotguns and cash, only to be caught by Big Chris, who seizes both the money and weaponry.
The power dynamics shift abruptly when Chris returns to his car, only to find Dog holding his son, Little Chris, hostage with a knife, demanding a ransom. Complying, Chris starts his vehicle and speeds away. Meanwhile, unaware of the grim situation unfolding, Gary and Dean stumble into Harry's office, leading to another bloody confrontation that ultimately claims the lives of Gary, Dean, Barry, and Harry himself.
After discovering the aftermath of the botched heist at their flat, the friends rush to Harry's office, where another grisly scene erupts. Without hesitation, they determine to claim the spoils for themselves. Yet, Chris has other plans; he runs them off the road, leaving Dog vulnerable, then striking a crushing blow with his car door. As Eddie grapples with the chaos, Chris manages to recover the money, allowing Tom to escape with the shotguns after a tense face-off.
Miraculously, the friends find themselves behind bars, only to be swiftly acquitted when the warden identifies Dog's gang as the true masterminds of the heist. Back at the bar, Eddie, Bacon, and Soap send Tom to dispose of the incriminating shotguns, unaware that Chris has stealthily pocketed the money. As the trio flips through an antique weapons catalogue, they are stunned to realize that their pilfered windfall holds far greater value than they ever imagined. In a panic, they try to contact Tom, urging him not to discard the shotguns. The film climaxes with Tom precariously balanced over Southwark Bridge, his phone ringing in his mouth as he readies to dispose of the incriminating evidence by throwing it into the River Thames.
