At the center of the violent, commanding English underworld flick "Gangster No.1" is an innovative and enticing bit of ironic casting. The story of a vicious mafia thug who hasn't changed at all in 30 years except to get more brutal and bitter, it features an unnamed title character played in two brilliantly vile performances by two sublimely in-sync actors.

Meanwhile, all the Gangster's acquaintances and enemies (he has no friends) change immeasurably over the years -- many of them trying to lead better lives -- yet they're all played by the same actors in both the film's 1968 past and 1999 present.

For director Paul McGuigan this is more than a gimmick. It's a metaphorical dichotomy with a resounding effect.

The preternaturally menacing Malcolm McDowell plays the Gangster in the present day, a cigar-chomping tough guy at the top of the criminal food chain whose greatest pleasure in life is that everyone he knows is scared to death of him.

But all his power and sway could get pulled out from under him in the next few days because his old boss -- the man Gangster tried to kill when consolidating power in his hungry and ruthlessly ambitious youth -- is getting out of jail 30 years after our boy framed him for murder.

Yeah, Freddie Mays is back, and despite living in Freddie's pad (decorated just the way Freddie left it) and running Freddie's empire for three decades, the Gangster is about to come face to face with the fact that he's still a pathetic wannabe, seething with 30 years of compounded psychological bile, and despite being the kingpin, he still has no idea who he is.

Flashing back to the late 1960s, McDowell narrates his rise to power over the chilling yet seductive performance of Paul Bettany (the wise-cracking Chaucer in "A Knight's Tale," Russell Crowe's impetuous roommate in "A Beautiful Mind"), who says only about one-fifth of what he's thinking, but does a spectacular job of expressing with his body language the venom in McDowell's voice-over.

From the day he's first hired by Freddie Mays (a surprisingly intimidating but still wiry and assailable David Thewlis), the Gangster has designs on the man's kingdom. "I was drunk on the smell of Italian leather," McDowell's voice hisses as Bettany surveys the mobster's designer high-rise condo like a circling hawk, imagining himself holding court on Freddie's plush couch, built into the sunken part of Freddie's shag-carpeted living room.

There are fierce plots and violent thoughts boiling behind Bettany's eyes in every scene of the movie's '60s and early '70s period. As the Gangster bides his time, he bites his tongue and holds his temper, even when Freddie's go-go dancer girlfriend (the stunning, statuesque and shrewd Saffron Burrows) spits in his face in response to a come-on. She's one more thing he wants to usurp from his boss, but he'd happily kill her just the same.

Director McGuigan demonstrates an impressive command of cinematic language in "Gangster No.1," shooting the 1960s scenes in a 1960s style and creating a vivid world of shark suits and babydoll dresses while photographing the modern era in crisp colors that pop off the screen. No less remarkable is the seamless age makeup used on Thewlis and Burrows, who in 1968 scenes look younger than they really are and in 1999 scenes convincingly play opposite the real, amazingly expressive wrinkles of Malcolm McDowell without raising a single eyebrow of doubt about their maturity.

But more importantly, McGuigan captures the pathological conflict within his title character. In his youth the man is hungry for everything Freddie represents. But when Freddie gets out of jail and has no plans to strike back -- in fact he's planning to marry Karen, the go-go dancer who has stuck by his side throughout his incarceration, and live a quiet life -- all the value Gangster assigned to Freddie's empire evaporates, leaving his ego without a rudder.

A warning to the squeamish: "Gangster No.1" spares the viewer nothing of its anti-hero's violent tendencies. In one scene, as Bettany consolidates his power, the camera takes the point of view of a rival racketeer being tortured to death by the Gangster. Bettany removes his expensive shoes and his expensive suit, folding it carefully, before taking axe, a machete and a hammer out of a leather bag. It's a disturbing, deliberately provocative moment that may cross the line for some moviegoers. But there's no denying it drives the point home since Bettany is literally whistling while he works.