Robert Rodriguez has completed two trilogies this year. July saw the release of the somewhat disappointing Spy Kids 3D (2003), and now he has returned to the movies which made his name: El Mariachi (1993) and its sequel/remake Desperado (1995), which launched his Hollywood career, along with those of its stars Antonio Banderas and Salma Hayek.

Rodriguez has been pretty prolific since his no-budget debut, though his films have never aspired to being better than the jokey cult splatter of From Dusk Till Dawn (1996) and The Faculty (1998), or the perky family-friendly fun of his Spy Kids movies (2001, 2002, 2003). His real newsworthiness lies in his production methods (as well as in his natural flair for publicity: the story that El Mariachi was made for $7,000 is such a good one that journalists are still quoting it, generally forgetting to point out the hundreds of thousands of dollars Columbia spent on post-production to turn Rodriguez’s film into a releasable product).

As a director, he has never lost his natural affinity with low-budget filmmaking, and his ability to make a little go a long way, when most Hollywood directors exhibit the reverse skill, has now carried him through eight and a quarter films (the quarter being his ill-judged anthology movie Four Rooms [1995]). Perhaps having had a glimpse of just how unwieldy film production can get if you let it, Once Upon A Time In Mexico reportedly marks something of a ‘back to basics’, having been filmed in only seven weeks in Mexico on the same hi-definition digital video system that George Lucas used for his recent Star Wars prequels (1999, 2002). And, as though this were one of his early no-budget productions, Rodriguez performed many of the behind-the-camera jobs himself: the opening titles claim that he not only wrote and directed the film, and designed the sets, but also "shot, chopped and scored" it too. And quite possibly bought the doughnuts.

And when those opening credits announce we are watching "A Robert Rodriguez Flick" it’s not too hard to work out what kind of a film this is going to be. Like its predecessors, it is all about spectacular gunfights, big explosions, and Antonio Banderas giving smouldering looks into the middle-distance while playing rippling chords on a Spanish guitar. If you turn up expecting anything else, you’re in the wrong movie theatre. We first find the Mariachi (Banderas) hiding out and brooding over the death of his wife (Hayek, who gets to kick ass in a long series of flashbacks) and child. Unsurprisingly, his retirement is shortlived, as he is recruited by a corrupt CIA agent (Depp) to intervene in an attempted assassination of the President of Mexico by an evil cartel kingpin (Defoe) who is hoping to install the renegade general who killed the Mariachi’s family…

Throw in a fistful of supporting roles, including Mickey Rourke with an incongruously funny-looking lapdog, and it’s clear that Once Upon A Time In Mexico is several degrees more complicated than its predecessors, and not always easy to follow. But the scrappy pacing and frequent flashbacks render the plot largely irrelevant, as does the occasional strain of Mexican populism that creeps into the script ("Who are you guys?" asks the President at one point, to be told by Banderas: "Sons of Mexico, Sir"). In the blowing-shit-up stakes, genre buffs will not be disappointed, although only the odd action sequence shows any originality. And, despite the title of the film, Rodriguez displays little affinity with Sergio Leone, whose similarly-set films are all about tension and release, rather than the big splurges of orange explosions and the hum of endlessly rattling machine guns firing off impossibly large numbers of bullets.

But what really sets this film apart, and makes it worth seeing, is the performance of Johnny Depp. On the basis of this and Pirates Of The Caribbean, he has a promising career (should he choose it) as a brilliant comic actor. Strutting around Mexico wearing a variety of ridiculous false moustaches and a t-shirt that reads "CIA – Cleavage Inspection Agency", Depp lights up the screen, hogs all the best lines, has some brilliant comic business with a prosthetic arm, and somehow even manages to tag some dignity to his venal CIA agent. The rest of the movie you’ll have seen before, somewhere or other, but Depp is something else.