WICKED Little Letters is one for all those who found Downton Abbey too stiff in the upper lip for its own good. Those who longed to see Maggie Smith drop an F-bomb at supper or Penelope Wilton call someone a ‘foxy-ass old whore’ over high tea. Can’t you just see the horror on Lord Grantham’s face?

From Me Before You director Thea Shamrock, Wicked Little Letters takes its cue from a true story that rocked the West Sussex idyll of Littlehampton through the early 1920s. Contemporaneously dubbed ‘the seaside mystery’ by The Daily Mail, the scandal saw local residents subjected to months of poison pen post.

While many in the town received abusive letters, the chief recipient was one Edith Swan, a pious and imperiously upstanding local. The insults were rotten from the start but grew in fruitiness with each new flap of the letter box.

To be called a 'cow' is one thing but to be told ‘the cakes you make look like they’ve fallen out of some ******* sheep’s ******* arsehole’…? Well, that’s something else entirely.

Much as such grotesquely must have horrified our Edwardian forebears, there’s little hiding the glee in an actor’s eyes these days when permitted to run riot with the urban dictionary. So it is here with Olivia Coleman, who plays Edith with all the relish of a star who’s been taping her potty mouth shut for years. Not since her Channel 4 days.

Around her, a who’s who of British acting talent, too, seize the smutty day. Timothy Spall, Gemma Jones, Joanna Scanlan, Jason Watkins and Eileen - three time Olivier winning - Atkins…all loving their agents.

Naturally, it is upon local Irish loudmouth Rose Gooding that suspicion quickly falls. She’s played by an on-form Jessie Buckley. It’s a case of prejudice over evidence, of course, but Rose has only WPC Gladys Moss (Anjana Vasan) in her corner.

While Agatha Christie’s The Moving Finger feels an obvious inspiration here, the mystery itself is no Marple. It won’t take an armchair Poirot to see through Jonny Sweet’s deceptions at lightening speed.

Nonetheless, there’s mileage enough in the efforts of Shamrock’s game ensemble to see you through. Wicked Little Letters isn’t quite the British comedy of the year promised by early trailers but can’t go far wrong with Coleman and Buckley at the helm. Watch the sparks fly.