It is often difficult to impossible to determine the truth of cannibal stories. Was there a Sweeney Todd? Did Ottis Toole eat up to 600 people in the US? How important to Jeffrey Dahmer was the cannibalism component of his murders? So it is for the older myths, such as that of Sawney Bean.

According to the mythology, Sawney was a Scotsman who, in the fifteenth or sixteenth century, moved into a cave in Bennane Head on the west coast of Scotland with his wife “Black Agnes” Douglas. They had eight sons, six daughters, 18 grandsons and 14 granddaughters, the grandchildren all being products of incest, since no outsider was found in the cave. Alive. Freud said that humanity’s “original” taboos were cannibalism and incest. Sawney won the daily double.

The Bean clan would ambush unwary travellers on the sparsely populated coast, but killing the victims and stealing their riches wasn’t enough to feed hungry, inbred mouths, because there were not a lot of pawn shops in the area, and eBay hadn’t been invented yet. Sawney’s revolutionary idea, a forerunner of modern serial cannibals, was take the bodies back to the cave and eat them, or preserve the flesh by pickling. The story goes that up to one thousand victims were so handled, making him, if real, the first and most prolific serial killer ever caught.

The reign of terror ended when a prospective victim escaped the Beans (although his wife did not) and alerted authorities. The king (possibly James VI) led a heavily armed party to capture the clan. Sawney and the men were condemned without trial and had their genitalia cut off and thrown into the fires, their hands and feet severed, and were left to bleed to death. After watching the men die, the women and children were tied to stakes and burned alive. By such methods is civilisation restored. Wes Craven based his film The Hills Have Eyes on the legend of Sawney Bean, it also makes a point about the vengeance of the civilised being as bad as the savage.

But, so the story goes, Sawney’s dying words were:

“It isn’t over, it will never be over.”

That’s where this film starts.

A descendant of the original Mr Bean now lives in Sawney’s cave, presented as the very image of a voracious mouth. The landscape here is a devourer, much like the peaks of the Andes, which looked like teeth in the movie Alive. Nature seeks to eat us up, from the bacteria and mosquito to the great white shark. We tend to see ourselves as outsiders to nature, at war with the natural world, but the cannibal reminds us that we are animals too, so he is, like nature, red in tooth and claw. Nature, like Sawney Bean, is indifferent to our pretensions of civilisation, merciless in killing and eating us (and this new Sawney likes a bit of rape too).

Lots of ultraviolence and growls and screams from Sawney’s hoodie-wearing kids.

Look, it’s a video nasty, which seeks to challenge the viewer with plenty of gore, shocks and carnage, and it succeeds to some extent. The plot has some annoying loose ends and is a bit thin, with sombre music announcing (as if we couldn’t guess) the forthcoming demise of anyone silly enough to wander around Scotland solo (which almost everyone in the film does at some stage). The acting is pretty great, particularly David Hayman, who has a ripsnorting and hilarious time as Sawney, spicing his cruelty with evil laughter. Like Sawney’s clan, the production seems to be a family affair, with direction by Ricky Wood, screenplay by his father Rick Wood and cinematography by his brother Ranald Wood. The cinematography is splendid, taking full advantage of the stunning scenery around Aberdeen and western Scotland.

The most scary image is Sawney’s mode of transport – a big, black British taxi. Those things terrified me when I was in London, and I can now see why. You get into one of those, and you might come out ready for Uber Eats.

Sawney also has a creature chained up at the back of the cave, and prepares tender morsels of brains, limbs, fingers and intestines, covered with “gravy” (fresh blood).

He hands the delicacy to his son, saying “give this to mother”. We eventually get to meet mother, and it doesn’t go well. How they made babies is hard to imagine. Maybe he slipped a roofie in her evening gore.

Sawney also tends to quote scripture and, like most who do that, picks the bits that suit him.

“Jesus said: unless you eat the flesh of man, and drink his blood, you have no life in you.”

The avenging hero is Hamish (Samuel Feeney), an investigative journalist with the requisite three-day stubble, an English accent and a Scottish capacity for alcohol. He goes to visit the Druid sacrificial site where the latest body was found, his girlfriend’s sister, or rather her head and someone else’s arms, all showing human tooth marks. He tells his recording device:

“Predatory killers often do far more than commit murder. Some have sexual desires, humiliation. They create gruesome rituals, as much for pleasure as for any other reason. This killer is not merely deranged, but evil.”

Well, maybe so, although the Bible-wielding Sawney would disagree. He feels that those he captures are fair game, prey for his hunters, and if he adds rape to cannibalism and murder, well, isn’t that pretty much what factory farms do, with their artificial insemination and culling?

No thriller would be complete without the bad guy spilling the beans to the hero, secure in the belief that he will soon be killing (and eating) the listener. Sawney tells the captive Hamish:

“You have to go back over 500 years and follow my bloodline. To the time when food was scarce, life was cheap, and only the ferocious survived.”

Then he’s back in the Bible, this time John 6:51.

“Any man who eats of this bread will have everlasting life on the bread that I give. This will be my flesh for the life of the world.”

And then verse 65:

“My flesh is meat indeed, and my blood is drink indeed.”

Yes, a favourite verse among Cannibal Studies scholars, and one that Sawney takes literally. He tells Hamish, as a slaughterhouse worker or a supermarket shopper might tell a pig,

“You’re just food, you’re a gift from God, which is who we are… You see, anyone can eat human flesh, you just have to make sure you wash it and garnish it well to avoid disease. Now, I particularly like the thighs and the calves… I prefer the taste of women to men, and I never eat hands or feet or testicles.”

Sawney would have been a hit as a judge on a cooking reality show.