Baird can be forgiven for a handful of careless and ham-fisted touches. Filth is still a hugely entertaining breath of foul air fueled by McAvoy’s impressively ugly star performance.

With McAvoy acting as if his life depends on it, Filth is the Irvine Welsh film we’ve been waiting years for. Tastier than a deep-fried Mars Bar.

A bulked-up James McAvoy dominates the screen in this razor-sharp Glasgow smile of a black comedy, packed with aberrant sex, hard drugs and maximum David Soul.

This punky adaptation of Irvine Welsh’s novel Filth is a glossary of grimness, a dictionary of darkness. But it also dishes up humour that’s blacker than a winter’s night in the Highlands and unpolished anarchy that’s true to Welsh’s out-there, frighteningly frank prose.

I loved every minute of Filth, and couldn’t have stomached another second of it.