Johnny Depp saunters into a London pub. He is surrounded by a giddy retinue of leering rogues who loudly chant “Johnny” and taunt him with provocative statements about his dwindling celebrity. Without reacting, he slumps into a chair, pulls some pornographic pictures from his pocket, gazes half-eyed around the room and slurs a barely audible response. His face is pale, his wrists limp, and his clothes slightly unkempt. He is, in the immortal words of his favourite Fast Show character Rowley Birkin, very, very, drunk.

He is also, of course, in character. For here, as the notorious 17th-century poet and drunkard John Wilmot, aka 2nd Earl of Rochester, in the scabrous tragicomedy The Libertine, Depp is deftly bringing the boozy reality of a self-tormented sot to screen.

It’s the sort of brashly entertaining study that seems to come effortlessly to Depp, having already mastered it in Fear and Loathing in Las Vegas, From Hell and even Pirates of the Caribbean. These characters are physical, witty and always compelling. But, most importantly, they come with essential dramatic catharsis and critical kudos inbuilt — Depp was, after all, Oscar-nominated for Pirates.

Similarly, look at Matt Dillon in this week’s quirky black comedy Factotum. The always reliable actor, gifted at deadpan comedy (To Die For) and drama (Crash), has been inundated with plaudits for this turn as the alcoholic Henry Chinaski, the fictional alter-ego of the Beat-era boozer Charles Bukowski. While, elsewhere, an Oscar nomination is almost guaranteed for Joaquin Phoenix’s portrayal of the oft ossified Johnny Cash in the forthcoming biopic Walk the Line.

And yet, ironically, there’s something overwhelmingly conventional about the screen drunk. Like the sombre cinematic portrayals of physical disabilities or terminal illnesses, the screen drunk has become a symbol of great acting — stick a bottle of Jack Daniel’s in my hand, push me over, and where do I collect my Oscar? (Step forward Nicolas Cage in Leaving Las Vegas.) It has become the performance equivalent of a rites of passage, and regularly attracts intense young actors eager to absorb by osmosis the genius of Bogart in The African Queen, or Nicholson in The Crossing Guard, or Streep in Ironweed.

“Life at any extreme is fascinating for actors,” explains the director of Libertine, Laurence Dunmore. “When you examine the human state at its most open, which alcohol tends to liberate, it makes a very appealing proposition for anybody who wants to express the full range of emotions.”

But it wasn’t always like this. There was a time when movies had a lighter, more cavalier, attitude to the demon drink. Early Hollywood stars such as W. C. Fields promoted the concept of the louche lounge lizard, even as his country was in the grip of Prohibition. His intemperate twinkly-eyed rake was a broad comedic precursor to Dudley Moore’s Arthur and even Richard E. Grant’s Withnail.

Later, in the movies of the legendary John Ford, mass consumption of alcohol was almost mandatory. Thanks to a romanticised notion of alcoholism, Ford lavished screen time on loveable drunks (usually played by that great ham Victor McLaglen), and often interrupted narrative momentum (see The Searchers) for boorish whiskey drinking and fist-fighting.

In 1950 James Stewart produced a finely nuanced performance, his own favourite, as a loveable lush whose best friend is an invisible rabbit called Harvey, but by the mid-1950s everything had changed. Billy Wilder’s account of the alcoholic writer Ray Milland’s journey into scotch-sodden oblivion, The Lost Weekend, heralded the arrival of the serious screen drunk. Milland, who ran the performance gamut from suavely inebriated to psychotic, won the Best Actor Oscar.

It was soon followed by the equally preachy Days of Wine and Roses, in which Jack Lemmon’s twitchy PR man turns his prim young teetotal fiancée, Lee Remick, into a cross-eyed slatternly lush. The pair endure all sorts of alcohol-related public humiliations until Lemmon comes to his senses and joins Alcoholics Anony- mous. Both actors were Oscar nominated for their “harrowing” turns.

From then on the model was set in stone. The ambitious Oscar-baiting screen drunk would simply follow the three rigid performance principles established by Milland and Co. First, like Meg Ryan in When a Man Loves a Woman, or Sandra Bullock in 28 Days, the drunk must demonstrate clear physical signs of inebriation, such as showy slurring, stumbling and incessant laughing at unfunny remarks. Second, like Nicolas Cage in Leaving Las Vegas, they must consume excessive and often unrealistic quantities of alcohol on camera. And finally, like Mickey Rourke in Barfly, or Kirsten Dunst in Crazy/Beautiful, the drunk experiences continual rejection from those around them until a dramatic closing scene offers either actual or a suggested redemption.

What these performances have in common is an urge to concentrate on the external signs of alcoholism over the internal dynamics of character. An urge to perfect the stumble rather than the stare. This, says Dunmore, is a classic actor’s mistake. “Drunkenness can become a performance tool, especially in terms of fictional characters. But it shouldn’t be about the physical effects of alcohol, but the combined effects of everything on the character’s personality.”

Occasionally, though, the screen drunk gets it right. And in fairness to both Dunmore and Depp, The Libertine mostly resists tendencies towards show-boating alkie shenanigans. Similarly, there has rarely been a more disarmingly frank exploration of the crushing banality of alcoholism than the indie icon Steve Buscemi’s Trees Lounge. Here the titular Long Island bar is home to an array of hardened drinkers, most of whom can converse eloquently, and have jobs and families, but nonetheless suffer from the debilitating disease of loneliness. It’s a tough-love portrait of life on the margins and a superlative example of where the screen drunk could go.

In the meantime, as long as actors continue to crave crude dramatic extremes and cardboard catharsis, and as long as the industry and the critical establishment continues to reward them for it, there’s little hope for the screen drunk. He or she is simply condemned to march into the dubious cinematic sunset of inane unthinking repetition, clutching vodka bottle in one hand and instant Oscar in the other. It’s enough to drive anyone to drink.

The Libertine and Factotum are on general release.