“I’m sorry... it’s all so sordid. What's the matter? I’m sorry... I had to see you, that’s all. I’ve been so miserable without you. Is it something I’ve done?”

Repulsion’s monochrome film stock suit the depressing mood perfectly, and it lends the whole thing an air of unreality that has you cowering in dread long before anything nasty actually happens.

Much like Peeping Tom (another essay in restrained psychosis) Repulsion starts with a big close-up of an eye. Unlike Peeping Tom, it's Catherine Deneuve's. She's Carol, a beautician in swinging London, and the film is concerned with chronicling her slow descent into madness.

Episodes with randy builders ("'Ello darlin', 'ow about a bit o' the other, then?"), cracked pavements and equally randy boyfriends all mix together to send the already monosyllabic young lady into murderous despair. Things aren't helped by surreal news items (the minister of health found eels in his sink) and her sister's energetic sex sessions in the room upstairs.

But things don't start getting really bleak until half way through the picture - pretty much dead on 45 minutes in, after Carol has been left on her own in the flat. Sis has been taken away on holiday ("Don't do anything I wouldn't do..." warns the sister’s boyfriend Ian Hendry - he has no idea). All of a sudden there's a loud cracking noise, followed by silence. A sign of Carol's increasingly fragile mind falling apart, or shoddy workmanship on the flat? There's no time to decide, because before you can say "whoah!" she's closed a mirrored door to reveal the reflection of a gurning figure standing behind her (a tired trope, but always effective). The figure is actually Mike Randall And Hopkirk (Deceased) Pratt, who was the randy builder from before, and it's not long before he's doing more than just scaring the pants off the audience. In the film's most unsettling moment (and there are lots of them), Carol imagines herself raped by him as a shadowy figure, who appears to roll out of her bedclothes. The attack happens in almost complete silence, with just the ticking of a clock heard.

Meanwhile Carol's sometime boyfriend Colin has decided he wants more than just to "give her one" (to use his friends' charming vernacular) and heads off to the flat to talk to her. After breaking the door down, he conducts this pathetic one-sided conversation with the now-mute Carol: "I'm sorry... it's all so sordid. What's the matter? I'm sorry... I had to see you, that's all. I've been so miserable without you. Is it something I've done?"

If she could speak (and still had all slates intact), I'm sure the conversation would have gone like this:

"I'm sorry..."

"What for? Breaking the door down? You bloody should be. We rent this flat, you know. That's going to cost an arm and a leg."

"It's all so sordid..."

"No it's not, it's bloody expensive. Do you have any idea what the word 'sordid' actually means? You bloody cretin."

"What's the matter?"

"You've just broken my door down, you complete arse!"

"I'm sorry, I had to see you, that's all."

"Well, that's alright then. By the way, in case you're too thick to realise it, I'm being sarcastic."

"I've been so miserable without you."

"Well I'm pretty miserable when I'm in your presence. Hence the locked door. And you've not improved the situation with this latest display, I can tell you."

"Is it something I've done?"

"No, of course not. You've just broken down my door and scared the shit out of me, it happens all the time. Don't worry, we've got a spare front door that we keep for situations like these, and I've been attending night classes in door fixing. You moron."

Is it any wonder she twats him one with the candlestick? (Glad to see it doesn't just happen in Cluedo).

Carol's mind has now completely snapped. The ghostly rapist makes repeat appearances (at one point to the sound of a kazoo), and the body count multiplies, the flat filling up with rotting food and dead blokes. Nastiest death of the lot (and one of the nastiest in Brit horror) is reserved for Patrick Wymark's seedy landlord, but I'll let you find out about that one yourselves. And I haven't even mentioned the shocking image of the grasping hands erupting from the walls.

Repulsion is brilliant. It's hard work, but worth it. See it, and be disturbed.