The crooks in London know how it works. No one carries guns and no one resists the police. Then a new gang appears that go one better. They dress as police and steal from the crooks. This upsets the natural order of the police/criminal relationship and the police and the crooks join forces to catch the IPOs (Impersonating Police Officers), including an armoured car robbery in which the police must help the gangs to set a trap.

A gang of hapless crooks, led by Sidney James, successfully perpetrate a robbery only to be caught after the fact. Fifteen years later they emerge from prison intent on retrieving their stolen loot - and discover a police station has been built over its hiding place.

An electrician boasts about being a cat burglar to impress his comrades, but his lie spins out of control when he's sought to participate in a jewel heist.