It is sometimes the case that when a promising filmmaker, having directed a much-heralded short film or two, is given the keys to a feature-length project, the results could be politely described as "hackwork", and unpolitely as "whoredom". Neither of these words apply whatsoever to Jane Campion, who followed up her highly successful run of idiosyncratic shorts made at the Australian Film Television and Radio School in the first half of the 1980s with 2 Friends, a telefilm made in 1986 and screened in that year's Un Certain Regard at Cannes - the same festival where her 1982 project "An Exercise in Discpline: Peel" won the short film Palme d'Or.

An unclassifiable film if ever I've seen one, the one thing that 2 Friends could certainly never be called hackery, though I would guess, if forced to, that the screenplay was handed to Campion - the writer, Helen Garner, never worked with her before or after, a unique situation in the director's career - yet she still made it her own. Even as her very first long-form narrative, there is a quality to both the matter and the presentation of 2 Friends that is unmistakably Campionesque; it is a clear extension of her earlier shorts, particularly "Passionless Moments", though it is tremendously inventive and unusual on its own right.

Describing the plot of 2 Friends is tricky, for reasons that will become quickly evident. The two friends, 15-year-old girls, are Louise (Emma Coles) and Kelly (Kris Bidenko), and they have known each other for years and years; and when we meet them, they're no longer on speaking terms, nor does it seem especially likely that they ever will be again. The reason why is, more or less, the raison d'être of the film, which moves generally backwards in time, in month-long chunks. That is, it moves back to the start of an earlier month and then show the month in regular, forward chronology, in this order: June, February, January, December, October. I'm making it sound harder than it is - I said it was a tricky thing to describe.

When we first meet these two, they are a study in contrast: Kelly is a right proper mid-'80s punk, with tattered clothes and wild hair, living in what sounds like it might be a commune but is probably just a group of druggies in an abandoned flophouse. Louise, meanwhile is... brown. That's the overriding image I have of her: mousy brown hair that just reaches the shoulders of her brown smock-like dress over a white shirt, with sensibly ugly brown shoes. While Kelly has dropped-out of nice society to pursue artistically evocative ways of destroying herself, Louise is new to a tony private high school, and that is the rub. For Kelly herself (we learn) also wanted to go to that same school, and even passed that school's rigorous application process; but her step-father (Peter Hehir) is a bit of a prick, and he won't let her go (for reasons that we don't learn for quite a long time, but tend to soften the impression we have of him by that time).

The film's bravura structure is its most noteworthy element, but it is no mere gimmick. This is not, Memento-style, a puzzle to keep us guessing, leaving us in the dark about key details until very late in the film. We know virtually all we will ever know about what "happens" in 2 Friends by the end of the first segment, 15 minutes into a 78-minute film; if there's anything that comes as a surprise from that point on, it's only that we learn more about characters, their motivations and reactions. Key to understanding what 2 Friends is, and how it works, is the film's very first scene: a girl (who we never meet) has died, and Louise's mother Janet (Kris McQuade) is attending her funeral. It is this event that causes Janet to start wondering about Kelly, once a fixture in her house, but gone these several months: is she headed for that same fate? Are her parents living every night with the fear that she's dead in an alley? What is she up to? These questions are all quickly answered to our satisfaction, if not Louise's, but the greater point is that we are, in essence, watching a eulogy: a memorial for a dead friendship. The rest of the film is therefore dedicated to showing not only how and why this happened, but much more importantly, why it is tragic. Each jump backwards carries us to a happier and simpler state in the girls' friendship, and we might think of this as the part of the eulogy that seeks to offer comfort in the solace of good memories: not for nothing does the film end on a frame of pure happiness, the most blissful moment in its entire running time.

Thematically, 2 Friends is akin to the short "A Girl's Own Story", an exploration of female adolescence that is primarily geared towards demonstrating the terror of that process. Structurally, it's more like "Passionless Moments": every incident in the film is isolated from every other. This is achieved largely through mechanical means - there is very little editing within scenes, and cuts are virtually never motivated by action, nor indeed by any other attempt to maintain continuity of space. The cutting serves, in other words, to divide the film up into tinier pieces, mostly unrelated to each other except by implication. That there is no real narrative throughline - events happen in a certain order, but not, generally speaking, does one event cause another; besides, the reverse-chronology would leave any "story" a bit of a shambles - lending the film a feeling more like a series of disconnected snapshots of particular moments along the way. This is true to some degree of all of Campion's earlier shorts, but in 2 Friends this idea is expressed to much stronger degree, simply because the canvass is so much greater.

Though clever and at times brilliant, the film is not without its significant flaws, and most of these are a result of some disconnect between the director and writer. Garner plainly has an idea that this is a partially class-driven story, which Campion does not deny; but at the points in the film where class issues enter the foreground, she clearly isn't certain what to do with it. This is most obvious in the scene where Kelly's step-father, Malcolm, reveals why he won't let her go to the school, for reasons of blue-collar solidarity; it is a moment that ought to humanise him, or at least make him seem more sensible than just a run-of-the-mill tyrant, but the moment is not directed to have the same impact that its position in the scene and in the narrative indicate that it ought. At other points, a similar problem rears up: Campion is interested in making a film almost, but not exactly overlapping the one that Garner wrote.

At the same time, most of what Garner wrote about characters, feminine identity, and growing pains all do fit neatly into Campion's program for the film, and these scenes are all magnificent. The two protagonists are drawn beautifully and played to near perfection; and the way that they're given weight in the story is tremendously interesting. Generally speaking, Louise is given more time onscreen, but the arc of the film is all Kelly's, so that while we are seeing more of the first girl, we learn much more about the other. Yet at the same time, this is not simply a matter of seeing Kelly through Louise's eyes, as evidenced by, chronologically, the last scene in the story: Louise reads a letter from Kelly, grows disinterested halfway through, yet we hear Kelly continue to speak even after Louise wanders off to do other things. It's maybe the best moment in a movie full of great moments, for it achieves at once two things: giving each girl a separate but equal place in the film's attentions, while suggesting that both of them are going to be okay - it will take some work, of course, but they can both survive; the worst is hopefully over, now that they've "broken up", as it were. There's a generous humanism about 2 Friends that is rare in cinema: rare because it is wholly sincere without being cloying, moving without being manipulative. Though often relegated to minor status in Campion's filmography, this is a striking and powerful debut feature for a woman who'd already proven herself something of a natural talent for the language of cinema.