British gangster movies have an advantage in shock value over their American counterparts: There's an element of politeness hardwired into the English personality -- even the cockney ruffians have it -- and so the underworld violence becomes an assault on civility from the inside out. Gangster No. 1 is a canny, derivative, wildly gruesome portrait of a London sociopath who's the scariest of sadists, in part because he's also a very courtly one. Malcolm McDowell, with menacing close-cropped hair, plays this elegant monster in the smugness of middle age, but the heart of the film is set in the late '60s, when he's a ruthless young climber embodied, in a mesmerizing performance, by Paul Bettany, the scalawag scene-stealer from ''A Beautiful Mind.''
Pale blond, with a shark bite of a smile and barely visible eyebrows that give him the look of a feral alien, Bettany plays the sort of fellow for whom crime isn't a means but an end. The crazier you think he's going to get, the quicker he ups the ante to the next level of artful viciousness. Bettany is presented as a real-life version of the droogs in ''A Clockwork Orange.'' A bit of the old ultraviolence gets his heart racing, but it's not reward he seeks -- it's consummation. Stunt casting aside, he and McDowell don't always seem like they're playing the same person, but Bettany gives you more than enough to watch.