Three of the gang masterminded by Pearly Gates (Peter Sellers) are in the middle of a robbery, stealing the mail from a post office van, but little do they know they are being watched. What appears to be a police squad car with three coppers inside trails their getaway car and when they get back to their base of operations, the "police" strike, taking away the loot and telling the gang members to stay where they are. But they soon twig that something fishy is going on when the coppers don't return for them - they've scarpered with the cash and London's criminal underworld are now subject to law-breaking themselves...
Does anything say Britain in 1963 quite like Peter Sellers doing the twist? Just one of the incidental pleasures of The Wrong Arm of the Law, a black and white crime caper filmed at the point where the U.K. was making the transition into colour. It makes up for the monochrome with a selection of vivid characters, with it's team of writers - including Tony Hancock's regular scripters, Ray Galton and Alan Simpson - offering up a wealth of juicy personality quirks and a fine ear for the vernacular, meaning this sounded better than many of the comedies of the period.
Sellers is ostensibly the star turn, but he's backed up with solid support from all quarters. We first meet Gates at his day job, selling frocks - sorry, gowns - to rich ladies and adopting a French accent to do so, all part of his charm. But when he gets behind closed doors, he reverts to his Cockney tones (a dig at then-renowed ladies' hairdresser Raymond Bessone), as he does when he finds out his gang have been fooled. There must be a traitor in their midst, but who? We find out early on it's Gates's girlfriend Valerie (Nanette Newman), but for some reason no one ever realises that she was informing for the fake police, not even at the end.
The criminal gangs of London decide to band together and see what they can do to stop the rip-offs, and it's a mark of the film's quality that even a talent like Dennis Price is allowed to light up the screen for a brief minute in a cameo, nominating Gates as the man to go to the real police with a proposal: they will stop illegal activity for a whole twenty-four hours to allow them to catch the impostors. But with a bungler like Inspector "Nosey" Parker (Lionel Jeffries on terrific form) heading the investigation, perhaps things might not go as smoothly as they would hope.
There is an abundance of idiosyncratic details guaranteed to raise a chuckle here, such as Bernard Cribbins as Irish criminal leader Nervous O'Toole having his watch stolen by his young son (twice), John Le Mesurier as the Assistant Commisioner enjoying his trip to the carnival a little too much having visited only as neutral ground to meet the gangs, or Parker blundering into the wrong apartment and being faced with a shocked Dick Emery about to conduct an affair. There may be echoes of The Lavender Hill Mob, particularly in its ending, and it might not be fall down hilarious, but with watching this is the overwhelming feeling of a job well done, and in that very satisfying indeed. Light and jazzy score by Richard Rodney Bennett.