Am I Being Unreasonable? review: Mumsnet beware, Daisy May Cooper is back to her abrasive best

“Am I being unreasonable?”, or AIBU for short, is the name of an infamous forum on the website Mumsnet, where parents can share their potentially controversial opinions. Now the ubiquitous phrase has lent its name to a primetime comedy - and a bracingly bold one, too. I look forward to Mumsnetters furiously debating its merits in posts beginning “AIBU or is AIBU a bit…”

Co-written by and starring Daisy May Cooper, who won a mantelpiece full of Bafta awards for rural mockumentary This Country, Am I Being Unreasonable? (BBC One) returns to the same Cotswolds setting - only for this whip-smart, grown-up comedy, Cooper has swapped teenage tracksuits for swishy coats and Smeg wine coolers.

The six-parter follows Nic (Cooper), an unhappily married mother-of-one - mainly because she’s privately mourning somebody she can’t speak about. So far, she’s managed to keep her dark secret hidden. When she spots a kindred spirit on the school run in Jen (co-creator Selin Hizli, Cooper’s real-life best friend), they instantly form a tight alliance. Can Nic trust this enigmatic new arrival?

Cooper has described the series as “genre-less” and it does resist categorisation. It flips from romance to thriller to horror, sometimes within the same scene. It’s traditional for critics to carp that it doesn’t quite succeed at any of them but that would miss the point of this endlessly surprising series.

Just when the show looks like it’s going to be about obsessive female friendship, it whisks the rug away. Nic’s grief, when revealed in flashback, provides a gut punch, while beneath all the mischief lies a poignant love story. Jump-scares jangle the nerves. Unreliable witnesses abound.

The casting and characterisation are ingenious. As Nic’s eye-rolling 8-year-old son Ollie, Lenny Rush is a revelation. Rush, who has dwarfism, has previously caught the eye in CBBC dramas and as Tiny Tim in Steven Knight's A Christmas Carol. Here he’s hilariously wise-beyond-his-years and an utter scene-stealer. Bafta-winner Jessica Hynes, meanwhile, pops up mid-series in a heartbreaking subplot.

Cooper struck gold working alongside her brother Charlie in This Country. She’s since struggled to replicate its success, with turns in middling sitcoms and generic panel shows. Wisely, she’s gone back to what she does best - creating something truly unique with those closest to her. She and Hizli are writing from experience, both having recently split from their partner, and they’ve clearly poured their souls into this. The pair’s on-screen chemistry is electric as they giggle, gossip and arrange children’s sleepovers, just so they can have a gin-soaked kitchen disco.

The schoolgates power-games recall a rural remix of Motherland, while the scripts are packed with knowing pop-culture references and are unafraid of a fart gag. Howls of laughter alternate with gasps of horror. Full of twists, turns and tonal gear-changes, Am I Being Unreasonable? is perhaps the most idiosyncratic home-grown series you’ll see all year. Try not to pigeonhole it or judge it simply as a comedy. Stick with it, strap in and relish the wild ride.

Am I Being Unreasonable? begins tonight at 9pm on BBC One; the full box set is on the iPlayer now