Inspired by a real-life scandal that rocked Britain in the 1920s, Wicked Little Letters stars Jessie Buckley and Olivia Colman in a black comedy that promises to turn the air blue and make your Aunt Nellie blush.

Scripted by Jonny Sweet, the film takes us to Littlehampton, the picturesque English coastal town where you’d expect everyone to be genteel and lovely. Except that behind the net curtains, residents are receiving the eponymous missives – insulting, anonymously written foul-mouthed tirades with more f-bombs than an Irvine Welsh novel.

Who is responsible for this shocking epistolary abuse forms the backbone of the film by Thea Sharrock, the British director who previously turned Jojo Moyes’s swoon-inducing Me Before You into a mega-hit.

The number one suspect is Rose (Buckley), an outspoken Irish immigrant and single mother whose arrival in the town has immediately stirred up suspicion from the residents, prejudices already stoked by the ongoing Irish War of Independence.

Attributing blame is her busy-body neighbour Edith Swan (Colman), who lives with her parents (Timothy Spall and Gemma Jones). While this spinster initially attempts to befriend Rose, the Irish’s mother’s free-spirited ways are at odds with Edith’s existence in a strict household, run by her brutal father’s iron hand.

As the accusations fly, Rose faces jail time, with the hapless coppers (Hugh Skinner, Paul Chahidi) seemingly unable to crack the case.

Only Gladys Moss (Anjana Vasan), Sussex’s first female police officer, has the smarts to think outside the box, believing Rose to be free of guilt. While the male contingent all but ignore her protestations, Gladys continues her own investigations. Credit is due to Vasan, who delivers one of the film’s better performances, both comic and earnest, as the Sherlock-like sleuth who must battle with the prejudices of the patriarchy.