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.
Peter Sellers
as Pearly Gates
Lionel Jeffries
as Inspector Fred 'Nosey' Parker
Bernard Cribbins
as Nervous O'Toole
Nanette Newman
as Valerie
Davy Kaye
as Trainer King
Bill Kerr
as Jack Coombes
Ed Devereaux
as Bluey May
Reg Lye
as Reg Denton
John Le Mesurier
as Assistant Commissioner
Graham Stark
as Sid Cooper
Martin Boddey
as Superintendent J.S. Forest
Irene Browne
as Dowager
