An American Werewolf in London is, for many people, a textbook horror film. It’s routinely name-checked as a stock favourite by fans and directors of the genre, successfully combining, as it does, visceral scares and belly laughs in equal measure. What’s odd though is that the film is a complete anomaly – rather than providing a boilerplate template for horror films it’s a giddy mish-mash of genres, styles and moods. It manages to take in an anglophile’s love of parochial Hammer horror, a stand-up fan’s worship of Groucho Marx’s razor-sharp banter, and a gore-hound’s joy at splattery, innovative special effects, all at the same time. Nonetheless it still coheres brilliantly into a thrilling piece of pure cinematic enjoyment.

John Landis, an absurdly precocious and talented young director at the time, maintains a vice-like grip on the tiller presenting a film that manages to be a love letter to its cinematic antecedents while never crumbling into pastiche. It is a taut, atmospheric horror; a ribald comedy shot through with sharp one-liners; a tender love story; and ultimately a tragedy. It shouldn’t work, but it most emphatically does, as a brilliantly weird, yet reassuringly solid film. Countless film-makers have tried to emulate it but few have come near. American Werewolf has become part of the lexicon of horror for a generation of film fans; a touchpoint that manages to encapsulate a world of crowd pleasing cinematic thrills into its idiosyncratic 90 minutes.

I first encountered the film as a nervous but curious kid, literally peeking through the crack in our living room door to illicitly watch a film I’d sternly been warned off by my parents. My Dad had mentioned how much he was looking forward to watching it, which naturally piqued my interest, but I was curtly informed that it was definitely not suitable for me. Which of course added fuel to the already flickering fire of curiosity in me. I planned on somehow seeing this adult horror film that promised so much from its strange title alone.

I hated sleeping at that age and was constantly bobbing back downstairs in my pyjamas with spurious reasons for being out of bed. It was a nightly, tiresome ritual for my parents to the point that I had managed to master the art of hovering quietly out of their periphery for long stretches of time. So it was the night that American Werewolf was shown, after the 9 o’clock news.

Already hyped at the expectations of what contraband thrills I could expect from a film that had been so firmly denied to me, I cautiously watched from behind the slightly ajar door, trying not to alert my parents. The film started.

The impact of the first 15 minutes of American Werewolf on my appreciation of horror films cannot be understated. From the opening shot, to the culmination of the attack on Jack and David this remains to me one of the perfect cinematic sequences. It doesn’t put a foot wrong building from a moody and restrained beginning through to an utterly terrifying climax. The first moment we hear a distant, muted howl from the relative comforts of inside The Slaughtered Lamb, we know the boys are doomed. The pair are tracked and stalked, the wolf coming ever closer with brilliant use of sound alone to create the building tension. Jack and David’s increasingly nervous banter dwindles as Landis ratchets up the fear.

I could, and do, watch it endlessly. The effect upon me as an 8 year old however, was seismic. At the point of the wolf’s frenzied, vicious attack on the likeable bantering American college boys I knew in an instant that my Dad had been right and that, yes, this was indeed too much for me. I scrambled up the stairs, Jack’s anguished screams still ringing in my ears. Buried under the covers I remember wishing fervently to un-see the sequence, to wilfully expunge it from my memory. To no avail, obviously. The sequence was seared onto my brain, the next few nights were sleepless. I strained at every gust of wind, every cat yowl outside.

One of the wonderful things about American Werewolf is the evocation of a specific time and place. For an outsider Landis does a remarkable job of capturing the colour and texture of Britain at the fag-end of the 1970s. From the establishing shots that capture the bleak, dreary majesty of the Yorkshire moors, to the multicultural vibrancy and grime of a London still shaking off the dregs of post-war despondency, the film is a fantastic cultural snapshot. Landis artfully sidesteps the usual pitfalls of an American’s view of Britain, but he still wrings some laughs out of the relentless stiff upper lips and weak chins of the English in the face of an increasingly out-of-control supernatural menace. This is a Britain that has disappeared and American Werewolf has become a surprisingly potent historical document of it.

Of course the film would not have so firmly secured its place in the horror pantheon if it wasn’t scary, which it most definitely is. Aside from the aforementioned opening scenes there are some truly iconic, perfectly executed scares. The isolated commuter waiting for the last tube home in a virtually empty underground station has a truly nightmarish quality; the fatal stumbling running up the escalator a standpoint of many a terrifying dream. The yuppies killed tantalisingly close to their home, the tramps taken out in the park – the wolf in this film is a vicious, primal thing that stalks and tears people apart in frenzied jump-cuts and pacey chase sequences.

The gore is vivid, and plentiful. Still today the film is surprisingly bloody and the final carnage-filled showdown in Leicester Square ups the ante to almost comedic levels. There’s an obvious glee to all this from long-time schlock fan Landis, but it’s never played for laughs specifically. Even the wonderful, surreal ongoing sight-gag of David surrounded by his ever-decaying undead victims is shot through with the gruesome realism of Rick Baker’s special effects. The sight of Jack’s exposed trachea undercuts the humour of Griffin Dunne’s droll, bemused performance. That dissonance is the film in a nutshell. You’re laughing, but at any point the whole thing could pivot into absolute horror, like the Nazi wolf-men that butcher David’s family in one of his lycanthropic fever-dreams.

American Werewolf is the best werewolf film. There’s some other good ones out there; The Howling, Ginger Snaps, Wolfen, and of course the original Wolfman. But Landis’ smart, assured, utterly unique film is the quintessential text. It’s one of the few horror films that retains the same power over me as when I first watched it. Age doesn’t diminish it and the potent alchemy that makes this weird, dissonant mixture of styles and tones coalesce remains elusive to other film-makers.

My own experience of seeing the film has become my personal ur-text for watching horror films. That perfect, crystal moment of transgression, peeking through a door at something that you shouldn’t be watching, but can’t stay away from.

“Stay on the road. Keep clear of the moors. Beware the moon lads.”

Beware the moon.