Ex-Lieutenant Colonel Hyde sends a copy of American crime thriller, 'The Golden Fleece', along with half a £50 note, to seven ex-officers. A letter accompanies the package explaining if the recipient wishes to obtain the other half of the money to come to the Café Royal, Regent Street at 1pm. The ex-officers (Race, Mycroft, Lexy, Porthill, Stevens, Rupert and Weaver) all have financial problems and are unhappy with their present situations.

After the ex-officers arrive at the café, Hyde reveals that all seven have guilty secrets that led to their dismissal from the services. Hyde's record is clean, but he feels bitter at his lack of reward for serving his country. He proposes the group should rob a bank, using their military training; each is a specialist in his own field. Hyde offers them £100,000 each if they agree to his plan, and says he will contact them again soon.

Race follows Hyde home, asking for a larger share of the money, but Hyde insists on equal shares for all. It is agreed Race can stay at Hyde's house. Hyde exchanges his Rolls Royce for a less conspicuous car.

The ex-officers meet at the New Gate Theatre Club where they pretend to rehearse Journey's End, but in fact discuss and agree to Hyde's plan. They report the next day to Hyde's house where they will stay for the duration of Operation Golden Fleece. Military rules are enforced, with fines levied for any breach in conduct.

Phase one of the operation entails stealing weapons from an army base. Irish accents are used to throw the blame on the IRA. One group, impersonating a commander and his retinue on an inspection of the base, creates a distraction, while other members of the League of Gentlemen pose as telephone engineers to steal the required arms. An AA patrolman spots their getaway car, but assumes they have broken down. He offers help, not realising the significance of the vehicle until later. The next day a newspaper reads, "Daring raid by Irish rebels. AA patrolman disturbs raiders."

Race and Porthill steal a truck for the robbery. Hyde reveals details of the plan, demonstrating a guarded delivery being made to the bank. The League will strike after the armoured car leaves. Weaver will knock out the bank's two alarm systems by detonating a bomb, while Lexy jams radio signals and Rupert creates a smokescreen.

As the League prepare in a warehouse, a local policeman dropping by panics them. The policeman offers to keep an eye on the place, but luckily does not appear to have seen any incriminating activity. Soon after Race arrives with a van stolen in broad daylight, to Hyde's annoyance.

The night before the robbery, Hyde runs through last minute preparations, burns evidence, and wishes the men good luck. Unable to sleep, Hyde and Race discover Lexy returning after a night out with a girlfriend. They impose a fine upon him.

The next morning the League robs the bank. The plan works, but a young boy noting down licence plates goes unnoticed. Back at the house, Bunny Warren, an old Army colleague of Hyde's, interrupts the League's parting celebrations. After many League members have left, Hyde receives a phone call from the police. Realising the game is up, he encourages Race to escape. Hyde and Bunny are arrested as they leave the house. The Sergeant informs Hyde the traitor was his own car. Both the young boy and suspicious policeman at the warehouse had copied down the offending license plate. Hyde and Bunny are led to a police van where the rest of the League, already captured, are waiting for them.