Charlie Croker, upon his release from prison, meets up with the widow of his friend and fellow thief Roger Beckermann, who has been killed by the Mafia in an Italian Alpine tunnel while driving a Lamborghini Miura. Mrs Beckermann gives Croker her husband's plans for the robbery that attracted the hostile attention of his killers, which details a way to steal $4 million in gold in the city of Turin and escape to Switzerland.
Croker breaks back into the toilet of his former prison to convince the powerful crime lord Mr. Bridger, a fervent British nationalist, to finance his Italian job. Bridger, who has bribed most of the prison guards to work for him, agrees after learning that Fiat is set to build a new factory in China.
With Bridger's backing, Croker recruits computer expert Professor Peach and a team of thieves and drivers. The plan calls for Peach to replace the programme in the computer that controls Turin's traffic control system, creating a paralysing traffic jam that will allow the thieves to escape with the gold in three Austin Mini Cooper S getaway cars.
After planning and training, Croker, his girlfriend Lorna, and the heist crew set out for Turin. They board the cross Channel ferry, MS Free Enterprise I to France. Mafia boss Altabani and his underlings are waiting in the Alps at the same pass where they killed Beckermann. Altabani warns Croker that the Mafia are aware of the gang's intentions and smashes their getaway cars (two Jaguar E-Type and an Aston Martin DB4 drophead) off a cliff. Just as Altabani is about to give the order to shoot the gang, Croker tells him that Mr. Bridger will avenge their deaths by driving Italian-owned concerns such as pizza restaurants and ice cream parlours in selected British cities out of business. Not wanting to risk suffering on any fellow Italians, Altabani lets them go, ordering them to return to England and believing that it is too big a job for Croker to undertake. Instead, Croker proceeds with the plan, and arrives in Turin. Prof Peach wanders off and gets arrested for molesting a woman on a tram.
The gold is loaded onto an armoured truck and drives through the city, escorted by an armoured car armed with a water cannon, two police motorcycles and police car. Altabani follows it in his car.
Croker replaces the traffic control system's magnetic tape data storage reels. On the day of the robbery, Croker sends gang member Birkinshaw, disguised as a football fan, to jam the closed circuit television cameras that monitor traffic. The substitute data reel then causes widespread traffic chaos. Croker goes through back alleys and courtyards in a Land Rover to avoid the chaos. The gang converge on the gold convoy, also utilising two car transporters, overpower the guards, and tow the armoured car into the entrance hall of the Museo Egizio, where they transfer the gold to the three Minis (red, white and blue). The police use one of the car transporters to try to smash down the doors. They enter too late. The majority of the gang redress as football fans and get in a minibus. Croker is in the red Mini driven by Dominic. The Minis rush around Turin and are seen in several iconic locations including the rooftop test track of the FIAT factory.
Altabani recognises that "If they planned this jam, they must have planned a way out." Pursued by the Turin police, the three Minis race through the shopping arcades of the city, speed down stairs, jump between rooftops, and finally escape the traffic jams by a pre-planned route across a weir. The getaway is timed perfectly, and they throw off the police by driving through a large sewer pipe. As Mr. Bridger receives the cheers and adulation of his fellow prison inmates, the gang drive the Minis into the back of a moving customised coach. They then unload the gold and dispose of the Minis by pushing them off the mountainside (the red one exploding spectacularly).
The rest of the gang, in the minibus, rendezvous with the coach in the Alps. On the looping mountain roads, driver "Big" William loses control of the coach. The back of the bus is left teetering over a cliff and the gold slides towards the rear doors. As Croker attempts to reach the gold, it slips further. The film finishes on a literal cliffhanger with Croker announcing: "Hang on a minute lads, I've got a great idea".
Michael Caine as Charlie Croker
Noël Coward as Mr. Bridger
Benny Hill as Professor Simon Peach
Raf Vallone as Altabani
Tony Beckley as Camp Freddie
Rossano Brazzi as Roger Beckermann
Maggie Blye as Lorna
Irene Handl as Miss Peach
John Le Mesurier as the Prison Governor
Fred Emney as Birkinshaw
John Clive as Garage manager
Graham Payn as Keats
Michael Standing as Arthur
Stanley Caine as Coco
Barry Cox as Chris
Harry Baird as Big William
George Innes as Bill Bailey
John Forgeham as Frank
Robert Powell as Yellow
Derek Ware as Rozzer
Frank Jarvis as Roger
David Salamone as Dominic
Richard Essame as Tony
Mario Valgoi as Manzo
Renato Romano(in Italian) as Cosca
Franco Norvelli as Altabani's driver
Robert Rietti as Police chief
Timothy Bateson as Dentist
David Kelly as Vicar
Arnold Diamond as Senior computer room official
Simon Dee as Shirtmaker
Alistair Hunter as Warder (cinema)
Lana Gatto as Mrs. Cosca
John Morris as Standin
Louis Mansi as Computer room official
Henry McGee as Tailor
Lelia Goldoni as Mrs Beckermann
Valerie Leon as Hotel Receptionist
Noël Coward, who played Bridger, was godfather of the director, Peter Collinson. Bridger's fellow convict and confidant, Keats, was played by Graham Payn, Coward's long-time partner. Lana Gatto was the nom de crédit of Hazel Collinson, otherwise known as Mrs. Peter Collinson. Michael Caine's brother Stanley Caine also appears as one of Croker's gang. The gang also included Robert Powell, in his first film role. Frank Kelly appears as an uncredited prison officer, also in his first film role.