In 1979, Martin Rosen, the writer, director and producer of Watership Down (1978), having decided, presumably, that he quite hadn’t traumatised us enough, started work on his follow up, again derived from a novel by Richard Adams. And this time, if anything, it was going to hurt even more. Published in 1977, The Plague Dogs was Adams’ fifth novel. Between Watership Down, his debut, and The Plague Dogs he’d published three other books (Shardik (1974), Nature Through the Seasons (1975) and The Tyger Voyage (1976), the latter with Nicola Bayley) but it was the anti-vivisectionist stance of The Plague Dogs that might have attracted Rosen’s attention.

Two dogs, Rowf (voiced by Christopher Benjamin), a Labrador-mix, and Snitter (John Hurt), a smooth fox terrier, are being experimented on in an animal research facility in the Lake District. Snitter has undergone never-explained brain surgery and is skittish and prone to bizarre behaviour, while the opening scenes find Rowf being drowned and resuscitated repeatedly by barely glimpsed “white coats,” the scientist who work at the facility. One night the dogs manage to escape, finding themselves on the barren moors without food and with no idea what to do next. They’re befriended by The Tod (James Bolan), a Geordie-accented fox, who teaches them to hunt but all the time they’re being hunted themselves – by the farmers whose livestock they kill for food and by the military, fuelled by rumours that the dogs are infected with bubonic plague…

Rosen, who again wrote the script as well as directing and producing, jettisoned some of the more satirical elements of the novel (in the book, the research facility was known as Animal Research, Scientific and Experimental, abbreviated to ARSE) and certainly had no truck with Adams’ happy ending, preferring instead a relentless and bleak tale of Man’s inhumanity to animal. And make no mistake, this is a tough watch. We frequently cut back to a close up of a traumatised lab monkey looking increasingly agitated as never seen scientists and Whitehall mandarins discuss the progress of the hunt and if you can’t get through these opening few minutes, where we see the animals in their cages awaiting who knows what fate (during their escape Rowf and Snitter find themselves inside a small metal room which we realise is the incinerator in which the bodies are disposed of), then you’d be advised to call it a day – this isn’t going to be the film for you.

Nor is it, despite the misleading advertising, a children’s film. Adults are going to struggle through this one holding it all together, God alone knows what it would do to younger viewers. And yet distributors MGM/United Artists decided to promote the film with the tag line “escape to a different world… and share the adventure of a lifetime” which suggests a very different and more family friendly film than we actually get. This isn’t “a different world,” it’s very clearly the bleak but very real autumnal world of the Lake District, the landscapes depicted as deliberately unforgiving and harsh though also instantly recognisable.

And as for the “adventure of a lifetime,” that’s hardly a fitting description of what our canine heroes go through on their journey. Left to their own devices, they revert to more primal ways, becoming killers of sheep and poultry in an effort to stay alive. The already deeply troubled Snitter is horrified when he accidentally causes the death of a human pursuer (he steps on the trigger of a shotgun causing the hunter to shoot himself gorily in the face), both dogs have been deeply and irreparably damaged by their experiences and in one scene, it’s strongly suggested that the dogs have eaten the body of another hunter who falls to his death.

There’s a sense of inevitability about the whole thing- death is everywhere, just one step behind the escapees and one can’t help but feel that they were doomed from the very start. To this end, Rosen decided to scrap Adams’ happy ending for something more ambiguous and certainly more haunting. The dogs are forced into the sea by approaching soldiers (the chase that leads them to the coast is as thrilling as anything you’ll find in a live-action film), Rowf forced to overcome his deep-seated fear of water. As they swim out towards an island that Snitter claims to be able to see, two shots ring out. They seem to miss, but the troops and the hovering helicopter guiding them disappear into a mist that rapidly descends around the dogs. They’re tiring, preparing to give up until Rowf announces that he too can see the island and they too disappear into the mist. It’s up to you to decide what happens – did the bullets hit their targets and the dogs are now dead, but still freed from their tormentors in a misty afterlife or did they really make it? Rosen leaves that up to you to decide. Stick around for the end titles and an island is indeed glimpsed through the murk. There is an island off that part of the coast, Kokoarrah, though whether in the film it’s real or a symbol of a better place for the dogs after their deaths remains ambiguous. It’s rather lovely really, a glimmer of hope after the relentless bleakness of the rest of the film.

The whole film is a veritable roller-coaster ride, never sentimental, never white-washing its more distressing moments but always remaining simmeringly angry about the circumstances that led the dogs to make their escape in the first place. Adams would remain a lifelong advocate for the welfare of animals and for care of the environment (when the film version of The Plague Dogs was released, he was serving a year’s presidency of the Royal Society for the Prevention of Cruelty to Animals (RSPCA)) and although the ending of the film deviates greatly from his book, he was apparently pleased with the way that Rosen decided to make things more ambiguous.

Less impressed was financier Jake Ebert who felt that the ending had damaged the film’s prospects at the box office. Certainly, it was far less well-received by the public than Watership Down, costing around £900,000 to make but recouping just £308,000 and it was less favourably reviewed by the critics. It was just too bleak for many it seems. Beautifully animated for sure, but that somehow just makes the horrors even starker and more unsettling. It’s not a fun film at all, and could leave you hating Mankind even more than eve. The horrors were softened very slightly for the American release which cut the film down from its original 103 minutes to just 86, removing the implication that the dogs had eaten the dead hunter and removing other bits and pieces in a doomed effort to make it a more child-friendly experience.

Heartbreaking, at times difficult to watch and with an ending that offers no easy way out, The Plague Dogs was always going to be a hard sell and while Watership Down regularly gets revived and introduced to another waiting-to-be-scarred-for-life generation, The Plague Dogs is far less widely seen these days. It remains however, one of the best – and arguably, given its subject matter, most important – animated films ever made.