It often seems, on a personal as well as cultural level, that the F-bomb has lost all power to shock.

And then a comedy comes along to remind us of the colorful ugliness and delicacy of language and how it can be deployed and censored to jolt, judge and control society. And where there’s judgement and control, there are insiders and designated outsiders, those who get the short end of the stick.

“Wicked Little Letters” is foul-mouthed farce based on a true “scandal” about a small town terrorized by vulgar, cruelly personal and utterly anonymous letters. In the hands of director Thea Sharrock, screenwriter Jonny Sweet and a sparkling cast, it becomes a parable on shifting social mores, sexism, morality confused with legality and women’s suffrage.

It’s a vulgar hoot.

Oscar winner Olivia Colman stars as Edith Swan, a smug, self-righteous spinster who starts many a remark with “If I were without sin” or “We’re all God’s creatures” and “It is in the pardoning that we are pardoned.” That’s usually followed by a moment of bringing the hammer down.

A lot of her blushing disapproval is aimed at her unfiltered, blowsy and blue-streak swearing Irish neighbor, Rose Gooding, played by brassy Jessie Buckley of “Wild Rose,” “Doolittle” and who co-starred with Colman in “The Lost Daughter.”

Rose is a widow, a single mum with a live-in lover (Malachi Kirby) given to singing and closing the pub down, a woman who swears like she breathes.

“You mangey old titless turnip!” is the most printable outpouring to emanate from her Irish-accented mouth.

Edith is sweet to her face, but behind her back she holds nothing back.

“She’s heinous!”

The furor really begins in 1920s Littlehampton when Edith gets her blush-inducing 19th letter from an anonymous critic. The obscenity has a studied, insulting air and a colorful variety and unfamiliarity with the form that suggests it was researched from a Roget’s Thesaurus of Vulgarity.

“You f—–g a-s old whore!”

Edith is wounded, her mother (Gemma Jones) takes the vapors. But her officious, ever-so-proper father (Timothy Spall) is apoplectic. He’s the one who goes to the police over this “prison offense!” And he’s the one who convinces the boy’s club of coppers (Paul Cahidi and Hugh Skinner) that these must come from their next-rowhouse-door neighbor, Rose.

Just like that, poor, powerless Rose, a “war widow” with a tween daughter (Alisha Weir), is arrested, charged and tossed in jail because she can’t make bail.

The cops ignore the fact that it’s a tad too-on-the-nose for the professionally-profane Rose to be the author of such screeds, that the letters continue and spread to the entire community, and that “Woman Police Officer Gladys Moss” (Anjana Vasan) has serious doubts about authorship and Rose’s guilt.

Director Sharrock (“Me Before You”) gets a lot of mileage out of the contrast between “Wicked Little Letters” and the “Downton Abbey” world she’s documenting, filling her supporting cast with screen veterans like Spall, Jones and Eileen Atkins, who have all appeared in their share of Dickens, Austen and Gilbert & Sullivan period pieces.

Some Brit journalist with a notebook in hand counted “120 outbursts” of colorful invective (Well done, you.) in “Wicked Little Letters,” readings from letters and insults delivered in the heat of the moment. That underscores the movie’s “We’ve kind of become numbed to it all” subtext.

Color-blind casting is applied to clever effect, emphasizing the hidebound, myopic Old Order challenged by the new, limited horizons broadened by taking women cops and characters with differing racial, cultural and social backgrounds’ views into account.

Women Police Officer Moss adorably enlists “friends” of Edith’s (Lolly Adefope, Atkins and Joanna Scanlan) in her investigation, even though she’s warned “women constables don’t sleuth.”

Buckley, a bracing breath of fresh air in many roles, gives Rose a resignation about all this that seems out of character but is a nice twist. Yes, she’s potty-mouthed and outspoken. But busted for it? “It’s a fair cop,” she seems to shrug, even as she insists she didn’t do the letter writing.

The “national” nature of the “scandal” is briefly touched-on, and we’re allowed just enough time to fret over whether justice will be done to keep things interesting.

And if the tale drifts into cute and finds a finish that’s a tad too pat, at least we have the satisfaction of muttering “About f—–g time.”

R: nudity, profanity

Cast: Olivia Colman, Jessie Buckley, Anjana Vasan, Lolly Adefope, Gemma Jones, Eileen Atkins, Joanna Scanlan, Hugh Skinner and Timothy Spall.

Credits: Directed by Thea Sharrock, scripted by Jonny Sweet. A Sony Pictures Classics release.

Running time: 1:40