‘The field … it’s covered in blood!” This is the young visionary rabbit Fiver, voiced by Richard Briers, in the British animation from 1978 by Martin Rosen, based on Richard Adams’s classic children’s book. The rabbits’ warren, quite as important as Tolkien’s shire, is about to be destroyed by a property development, announced by the humans’ heartless wooden sign, which of course none of the rabbits can read, but twitchy, squirming Fiver can sense the disaster it represents.

So his brother Hazel (voiced by John Hurt) leads Fiver and a breakaway gang on a quest for safety to far-off Watership Down, a rumoured place of sanctuary foreseen by Fiver; they include hot-headed Bigwig (Michael Graham Cox) and later the once hostile Captain Holly (John Bennett), a traumatised survivor of the warren’s destruction. But the band of lapine brothers are to confront tyrant-warlord General Woundwort (Harry Andrews), a terrifying figure in keeping with the film’s 70s type post-apocalyptic atmosphere. Yet they find an unlikely ally in a squawking gull called Kehaar, voiced by Zero Mostel. The vocal talent in other roles is a roll-call of blue-chip character actors: Denholm Elliott, Ralph Richardson, Michael Hordern and more.

This animation was in the news recently because the British Board of Film Classification decided to up its rating from U to PG due to the red-in-tooth-and-claw violence that the film shows. And it is indeed very shocking: Bigwig is almost throttled by the wire snare, and Holly has a horrible account of stifling in the burrow blocked by dead rabbits’ bodies. There is also the rather louche and adult moment, when Bigwig, having infiltrated Woundwort’s community pretending to be a volunteer, is coolly offered any doe he wants. Another very disquieting scene is the encounter with Cowslip (Elliott), whose warren consists of sickly rabbits, dreaming listlessly of death and dully inviting Hazel and his friends to join them; they are being secretly fed by humans who want to eat them. (Watching this movie now, I was reminded of the scene in Cormac McCarthy’s The Road with the zombified people who are imprisoned and kept alive as cannibal food.)

Watership Down is in fact a film very much concerned with spirituality and the afterlife, with a Kiplingesque story at the very beginning about how the rabbits came to be, with a belief system that has the Frith god at its centre and his angel of death, the Black Rabbit. The awful possibility that Hazel might have died is what ushers in Mike Batt’s hit song Bright Eyes. The animation reportedly disappointed some at the time, for its lack of expressiveness compared with Disney figures; it’s fair to say the rabbits are impassive compared to Bambi’s Thumper, and perhaps the film doesn’t have the richness of Adams’s book. But now they seem to possess a charm and simplicity, and perhaps Rosen’s animation style was the closest Britain came to a homegrown Studio Ghibli.

• Watership Down is in UK and Irish cinemas on 25 October.

• This article was amended on 23 October 2024. An earlier version referred incorrectly to “Michael”, rather than Martin, Rosen.