I never saw the first film with the title Bad Lieutenant , and director Abel Ferrera having declared that he wishes death for the team involved in the new one only makes me think that he’s a juvenile prick whose work I have no desire to see. Besides, having caught Bad Lieutenant: Port of Call — New Orleans, I cannot but see Nicolas Cage as synonymous with that job description, and director Werner Herzog as brilliant for having conjured such a magical performance from him. Without their alchemical teaming, the film would have attained nothing more than formulaic edginess, the kind of stuff that used to be called Tarantino-esque.

Would you believe a film about a maverick cop could be original? Terence McDonagh’s descent into crazed evil starts with something as innocuous as a bad back, for which he needs prescription drugs. At a symbolic level, the spine is how a man becomes and stays upright. Pretty soon the lieutenant has one shoulder hunched above the other, and is using whatever illicit drugs he comes across to keep the pain at bay, in the process foggying his perceptions and bringing out a more primal aspect of his character.

So far, so what? Well, it’s all about the execution. Cage is on fire throughout, every time you think he’s reached a new depth plummeting further still with an even more grotesque act, freefalling through badness and madness while still somehow remaining a cop smarter than his colleagues. In a medium where maverick generally indicates two days of stubble and a preference for classic cars, Lieutenant Terence McDonagh is a truly impressive creation.

But hey, is McDonagh born bad, or is he made that way by his environment? Post-Katrina New Orleans is the perfect setting for this litany of decay and corruption, the landscape itself traumatised. It’s notable that the one truly selfless act McDonagh does is to rescue a prisoner in a cell where rising riverwater threatens to kill him, if a poisonous snake doesn’t get him first, launching into the murky water even though he’s wearing $50 Swiss cotton underpants. That act of charity comes back in fascinating form at the film’s cryptic conclusion.

The snake is a good indication of life being out of kilter, and it’s joined by an alligator and an iguana that’s real to the drug-fuelled McDonagh but invisible to his colleagues. The wildlife could be read as a measure of the balance between man’s civilised world and the feral one that co-exists alongside it. In this regard it’s interesting that one of the more touching moments in the story is when McDonagh finds a murdered child’s pet fish, and the poem he wrote about it for class. That and the ‘treasure’ McDonagh found as a child — a tarnished silver spoon he believed to be part of a pirate horde — are where the film’s surprisingly tender heart lie.

But hey, this is Bad Lieutenant, and we want to see crazy stuff. Which we get plenty of, in achingly and darkly funny scenes: McDonagh doing a foulmouthed interrogation of a congressman’s senile mother and her devoted carer, while pulling the oxygen tube away from the former, has to be the most twisted thing I’ve seen in a good while. Believe me, there are plenty of other choices if that one doesn’t tickle your funny bone, and Nicolas Cage isn’t the only larger than life character: he is the most extreme figure in a world where extremes — of violence, of drug abuse, of venality — are the norm.

Anchored by Cage’s performance, this is very much a character-driven film. Sure, there is an interesting story too, about how the cop brings to justice a multiple murderer, and for all the fireworks that plot has farily rigorous attention paid to it throughout: kudos to scriptwriter William M. Finkelstein. But fundamentally this is a film in which an actor and director at the top of their games spur one another on to great things, and that’s always a cause for celebration.