“I feel that the world is such a nice place, with so many good people and acts of kindness happening every minute,” said no-one ever after watching a film based upon one of Irvine Welsh’s books. After sitting through the 97 minutes of his latest contribution to cinema, ‘Filth’, I was thoroughly deflated about life in general. It wasn’t as if I didn’t know what to expect; ‘Trainspotting’ remains one of the weirdest, most mentally-challenging films I have ever watched to date. The ‘18’ certificate for ‘Filth’ was a warning klaxon in itself. Films nowadays have to earn this rating by containing extremes – extreme horror, extreme violence, or extreme sex. And in this case, it seemed to be a combination of all of the above.

The film follows the life of rogue police officer, Bruce Robertson (played by the brilliant James McAvoy) who has set his sights on earning the promotion to Detective Inspector available in his force. His competition though, remains tough, and he is prepared to go to any lengths to secure his success. When he is appointed leader of a murder squad to trace a Japanese student’s killers, he sets about proving that he is worthy of the job. Bruce, to say the least, would be the last employee the UK Police Force would use to drum up new recruits. Unless those new recruits wanted that life of whisky, vomit, sadomasochism-with-your-colleague’s-wife, whisky and homophobia.

But this wouldn’t be an Irvine film if it didn’t include the mandatory sex, drugs and rock’n’roll. (Mind you, not so much of the last one however, as it is set in Edinburgh.) The audience is exposed to a dirty underworld in the police force, one that is reeking of corruption and cocaine. It soon becomes apparent that Bruce is fighting his own personal battles, too, with visits to psychiatrists and prescribed lithium medication. The film slowly progresses further and further away from reality, with frequent surrealist interludes. Allusions to Bruce’s family and murky past become a recurring motif and partly explain why his methods of work are so nasty.

Yet, in uncanny dualism, we also begin to see a vulnerable side to the brutal officer. His softness for a lady he meets in a chance event becomes apparent, and as his descent into partial drug-induced mania becomes more rapid, the audience is compelled to re-evaluate their opinions of him. The film ultimately becomes an in-depth profile of a downward spiral, and despite Bruce’s highly distasteful characteristics, McAvoy manages to somehow evoke sympathy for his character. The twist at the end is unexpected and perfectly executed, even prompting applause from my audience.

This film is, simply put, filth. Bruce is the definition of filth (albeit in an unexplainably sexy way). One thing is for sure: I’m glad I had eaten most of my pick’n’mix before the opening credits because the very thought of eating whilst watching this film is enough to make my stomach churn. Whilst I’m not a complete prude, watching a young girl being coerced into performing a sexual act on Bruce is highly uncomfortable viewing. The gritty realism typical of Welsh’s output is all too present. Like the traumatic scene involving Ewan McGregor’s cold-turkey spell in his childhood bedroom in ‘Trainspotting’ (in my opinion one of the most harrowing cinematic sequences), there is a particular set-up involving Bruce’s naïve ‘friend’ taking drugs for presumably the first time and thus experiencing a harrowing come-down. Show this to a group of impressionable teens who view drugs as a world of glamour and you will be guaranteed to put them off the Charlie for life.

Just when you thought it was safe to go back to the cinema, Welsh wallops you in the face. But ultimately, you leave the cinema thanking God that you aren’t living the kind of life depicted on screen. It’s refreshing, but in possibly the foulest, filthiest way.