I watched Filth from behind my hands. It’s ghastly and unpleasant, but what I saw of it was brilliant

People are generally saying Filth fully fulfils the promise of its title and is not for the faint of heart or queasy of stomach or lily of liver and, alas, I am all three, in spades. (My liver is, in fact, so lily-ish it may be a wonder of medical science.) Rape. Anal Sex. Violence. Drink. Drugs. Masturbation. Vomiting down yourself. There’s a part of me that would like to say that’s the average Saturday night in our house, but the truth is we generally watch The X Factor and record Strictly. So I endured this film, from behind my hands, rather than enjoyed it, but in the enduring, was there some reward, as can sometimes happen? We can work that out as we go along. No advantage in rushing such things.

Based on the Irvine Welsh novel of the same name, it stars James McAvoy, who I should say, straight off, is absolutely terrific, and may provide the strongest reason for sitting through this. McAvoy plays Bruce Robertson and Bruce Robertson is Filth. He’s Filth because he’s an Edinburgh cop, and one of the nicknames for cops is ‘filth’, and he’s filth because he is repellent; a brutal sociopath with no moral compass. He is racist, homophobic, misogynistic, vindictive. If he’s not shoving coke up his nose he’s drowning in whisky. He torments then sleeps with his best friend’s wife (the magnificent Shirley Henderson, with a Cheryl Cole hairdo) and demands blowjobs from underage girls. He has no interest in solving crimes, particularly as he is otherwise preoccupied with gaining a promotion ahead of his colleagues, a darkly comic bunch which includes his coked-up sidekick, Jamie Bell, and, worst of all, not just a woman (Imogen Poots) but a woman who sees right through him, to what?

This is as much a journey through one man’s mind as it is through Edinburgh’s dark underbelly of general horridness and all the bodily fluids you can think of, plus quite a few you didn’t know the body actually produced.