Adapted from Irwine Welsh's third novel, Filth is the story of Detective Sergeant Bruce Robertson (James McAvoy) a depraved, alcoholic, drug-taking, sexually aggressive, manipulative member of Edinburgh's Lothian constabulary. Eagerly hoping for a promotion, willing to eviscerate his colleagues in order to achieve it, and cack-handedly investigating a murder.

There's not that much more to the general narrative of the film than that, this is, undoubtedly, McAvoy's show and he dives into the role with gusto. He manages - to a reasonable degree - the tricky balance of making Robertson a fascinating screen presence, utterly unlikable yet you oddly invest in his tale, in the vein of Christian Bale's Patrick Bateman from American Psycho.

To maintain the audience's empathy he's surrounded by a gallery of other unlikables, most notably Jamie Bell as his colleague Ray Lennox an insecure, yet equally addled character, and the cartoonish Clifford Blades (Eddie Marsan) a thick-rimmed, naive "friend" of Robertson's whose wife Bunty (Shirley Henderson) is plagued by a prank caller. Elsewhere the rest of the police department is peopled by broad caricatures, as well as Imogen Poots as Amanda Drummond, who gets the rather thankless role of being the voice of reason.

Whilst the actors are game the film is let down by lacking a distinctive voice of its own, stylistically it's a hodge podge of recent fare such as Martin McDonagh's In Bruges and John Michael McDonagh's The Guard, whilst there are distinct whiffs of A Clockwork Orange, The Rules Of Attraction and Dennis Potter. Additionally, the film wavers awkwardly around Robertson's backstory, creating awkward moments of 'understanding' that are strangely irrelevant, like Bateman it'd be nice to have a character who doesn't have some tragic history that made them the way they are.

These inconsistencies in style are further reflected tonally, whilst at times it seems the film is striving for a heightened, cartoon-like satire at others it seems to be gunning for gritty anti-hero bite, and then it veers into poorly realised fantasy, or lurches into despondent drama. If this felt like it was more reflective of Robertson's fractured psyche then it wouldn't jar so awkwardly, alas it feels uncertain and often misjudged.

At its core the film seems to have the best intentions, a rambunctious desire to be gleefully provactive and hold a funhouse mirror up to those members of society and service that we're supposed to see as "righteous", but, ultimately it lacks in vitriol, wit and energy, winding up oddly dreary and sluggish.