Synopsis
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.
Cast

Peter Sellers
Pearly Gates

Lionel Jeffries
Inspector Fred 'Nosey' Parker

Bernard Cribbins
Nervous O'Toole

Nanette Newman
Valerie

Davy Kaye
Trainer King

Bill Kerr
Jack Coombes

Ed Devereaux
Bluey May

Reg Lye
Reg Denton

John Le Mesurier
Assistant Commissioner

Graham Stark
Sid Cooper

Martin Boddey
Superintendent J.S. Forest

Irene Browne
Dowager

Arthur Mullard
Brassknuckles

Tutte Lemkow
Siggy Schmoltz
Dermot Kelly
Misery Martin

Vanda Godsell
Annette
Barry Keegan
Alf

Marianne Stone
Woman at Meeting (uncredited)

Michael Caine
Police Officer (uncredited)

Dennis Price
Educated Ernest (uncredited)

Dick Emery
Adulterous Man (uncredited)

John Junkin
Maurice (uncredited)

Cardew Robinson
Postman (uncredited)

Mario Fabrizi
Van Driver (uncredited)
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