“Censor” is a horror satire about one of those intrepid, iron-stomached bureaucrats of the British Board of Film Classification, a woman who brings a zeal “to protect people” to her job in Margaret Thatcher’s Britain.

It’s the mid-80s, and the Fleet Street press and the public are in an uproar over the invasion of “video nasties,” extreme horror that was making its way around the censors, into stores and into the hands of children and the criminally suggestible.

Enid Baines sees herself as the last line of defense against a sea of sadistic blood and gore, movies that the public is sure are leading to imitation by the nation’s most heinous criminals.

Niamh Algar, of “Calm With Horses” and “Wrath of Man,” plays the censor her colleagues label “Little Miss Perfect.” She takes notes, watches and rewatches scenes, pushes back against the permissive posh (Nicholas Burns) they usually pair her with, a snob who dismisses this disemboweling or that rape as “nothing” or worse yet, “art.”

Enid is a loner, pretty enough to constantly be hit on by men, including the creepy producer Doug Smart (Michael Smiley, wonderfully oily) who’s always trying to “get a 15” (approval for watching by ages 15-and-up) rating for the sordid B-movies he puts out. Enid is immune to everyone’s charms.

Because Enid is focused on the work, driven by a trauma of childhood to treat her job with a missionary’s zeal. We learn about that at pretty much the same time that it all goes wrong. There’s a gruesome crime and the press ties it to a movie that Enid “let in” (with edits).

Somehow, they know not-quite-anonymous censor approved this particular “nasty,” so the harassing phone calls and scrums with the pushy press at her door begin.

That stress is the perfect thing to plunge her into an obsession over a horror actress (Sophia La Porta) who looks too familiar, whose movies seems to echo the great tragedy of Enid’s guilt-ridden childhood.

The Irish Algar is at her most buttoned-down here, hiding the “pretty” with “prim” and not wholly succeeding. She’s got standards — insisting, like Hitchcock, that “somethings should be left to the imagination.”

Eye gougings and rapes, axe murders and “tug of war over his intestines” are but some of the lines Enid draws in the sand.

But Algar, as she’s proven in film and on TV (“Raised by Wolves,” “Pure” and “The Virtues”), is adept at both overtly demonstrating a character’s edge and baggage, or leaving the merest suggestion of it in her performance.

“Censor” is a slight and obvious slasher film whose satiric points are both slapped-down and endorsed. Maybe violent cinema is twisting our heroine just as she worries it is twisting the public.

But the stern star and fascinating if limited peek into the world of ratings, even in a period piece set in a more conservative time, makes “Censor” a horror title well worth a look, “video nasties” included.

MPA Rating: unrated, graphic horror violence

Cast: Niamh Algar, Michael Smiley, Clare Perkins, Sophia La Porta and Adrian Schiller

Credits: Directed by Prano Bailey-Bond, script by Prano Bailey-Bond and Anthony Fletcher. A Magnolia/Magnet release.

Running time: 1:24