“Send advance parties immediately. Have now established humans high in protein… and easy prey…”

A cannibalistic alien half man half dog who shares a house with a lesbian couple - it would make a great Channel 4 sitcom.

But stand down, Channel 4, because someone’s already done it.

Prey is a bizarre offering from the bizarre mind of director Norman J Warren (Terror, Inseminoid). Part exploitation, part melodrama, but definitely not (intentionally) funny.

The film starts with Kator, an alien, arriving on earth and immediately murdering a courting couple and three rabbits.

Living in the woods nearby are Jessica and Jo, who, after hearing radio reports of "lights in the sky" during the night, go to investigate and find the bodies of the three dead rabbits.

We’ve already been shown that their relationship is not in the best of places, and things take a turn for the worse when they meet our hungry alien friend (who's hurt his leg, poor dear) and decide to take him home. They don't seem to even notice his odd behaviour, even when he says his name is "Anders… erm, Anders Anderson."

Kator decides to return to the scene of his culinary crime, and finds a couple of policemen investigating the murder scene. They chase him, and he turns into a weird dog-faced creature before messily despatching them.

It's worth mentioning at this point that although all these goings-on sound pretty daft written down, the film is so nicely shot, low key and leisurely paced that it's strangely believeable. And because Kator's real appearance is kept as a sudden shock, blink-and-you'll-miss-it effect, it's not that bad.

This being 1977, there’s some whiffy sexual politics going on which these days raise more of an eyebrow than the extreme gore. Sometimes it feels like all the film is lacking is a huge neon sign screaming “lesbians!”

"I think you should know that Jessica and I are lovers," Jo announces smugly at the dinner table that evening. This doesn't quite have the effect she was looking for - Kator simply spews up his meal (it appears he can only stomach raw meat).

This doesn't put Jessica off, "He's very attractive," she confides in Jo. "For a man, I mean…"

"I think that man is contaminating you, Jessica," Jo replies.

Just to reinforce the point, we then get a gratuitous sex scene, the girls making up after their argument watched from the shadows by a blank-eyed Kator.

"Have made contact with human life forms," he reports back to base. "New identity established."

Oh - oh.

The next day they awake to find that all the chickens have been killed, and this time it really is the work of a fox. Jo vows to find the beast and kill it with a variety of traps, which is, let's face it, not a very vegetarian thing to do. But she fails, and the next thing you know Kator turns up with the beast's body. "My way of thanking you…" he explains, in monotone.

The three of them celebrate by having a party, which involves Kator getting dragged up (the look on his face is priceless) and a quick game of hide-and-seek, during which Jo inexplicably arms herself with a big knife. But not much comes of this, although the next morning Jo tells Jessica: "He's dangerous! I think he's mad!"

Then waving the half-eaten remains of the fox in front of her lover's face, she adds: "He's an animal! You must believe me…"

Before either of them have time to act on this, Kator falls into a very muddy pond whilst trying to access an "alternative food source" (swans - perhaps he's royalty?) and has to be rescued by the pair, in a scene which goes on far too long (much thrashing around ensues).

Jessica seems to have misinterpreted Jo's warning as being some kind of recommendation about their guest's sexual prowess, because it ain't long before she's decided to leave Jo and run off with her slightly odd new friend. And we're set for what can only be described as a very nasty ending.

Without wanting to give the game away for anyone wanting to watch this, I think it's fair to say that the majority of Prey's budget must have been spent on the (literally) stomach churning effects at the end. But also watch out for one of the best examples of projectile vomiting ever seen in a British horror film.

Strangely, despite all the killings, Kator comes across as being actually quite a nice bloke. After all, he's only doing his job…