Put yourself in Terry Gilliam's shoes for a moment. As the director of the hugely anticipated adaptation of Hunter S. Thompson's classic counterculture novel, you are handed a project which has been branded "unfilmable" by Hollywood for more than quarter of a century, a budget which requires the aid of a magnifying glass, one previous owner - Brit director Alex Cox who jumped ship when the oft-cited "creative differences" reared their ugly head - and an absentee landlord in Thompson himself, whose main interests amount to drinking heavily, firing shotguns or doing both simultaneously.
In the face of such insurmountable odds, Gilliam has bravely chosen to spike his film: it looks great, it gives you the giggles and it bends your mind. But unfortunately, when the lights go up, you're left with a headache.
The plot, which generally takes a backseat to some magnificent images, follows sports writer Raoul Duke (Depp) and his Samoan attorney Dr. Gonzo (Del Toro) travelling to Las Vegas in 1971 to cover the legendary Mint 400 desert motocross. Not that much reporting gets done: for these boys are fully-fledged, card-carrying drug enthusiasts who swallow a suitcase of illegal pharmaceuticals and wander down the Vegas strip as if it were Hell on earth.
The fact that anywhere on earth would resemble Hell if you digested 73 pellets of mescaline, a salt shaker full of cocaine and a pint of raw ether goes unnoticed because Gilliam has crafted scene after scene of hallucinatory brilliance, some of which - melting carpets, a literal lounge lizard attack - ranks among his most bizarre and best imagery to date.
The film itself, though, crumbles into oblivion through heavy symbolism (the American dream is blatantly represented as a wasteland of car wrecks) but still manages to maintain its shape even while melting, thanks to two exemplary performances: Depp progresses majestically through the picture like the author's clone - bald head, filtered cigarette, manic gestures - pulling out that little bit extra with a droll narration. Equally stunning, Del Toro's massive 45-pound beer gut and vomit-flecked hair goes far beyond the call of thesping duty. Both actors are world class in a film that squeezes your pleasure pads and wrings your brain but ultimately fails.