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
Lionel Jeffries
Bernard Cribbins
Nanette Newman
Davy Kaye
Bill Kerr
Ed Devereaux
Reg Lye
John Le Mesurier
Graham Stark
Martin Boddey
Irene Browne
Arthur Mullard
Tutte Lemkow
Dermot Kelly
Vanda Godsell
Barry Keegan
Marianne Stone
Michael Caine
Dennis Price
Dick Emery
John Junkin
Cardew Robinson
Mario Fabrizi
John Harvey
Harold Siddons
Jack Silk
Deryck Guyler
Gerald Sim