Yanks buy stacks of tickets in the West End. Why is Made in Dagenham so rude to them?

Go slow at Dagenham. The musical based on the film about a pay dispute in the 1960s starts as a sluggish mire of twee simplicities. We’re in Essex. Grumbling Cockney wage slaves inhabit cramped but spick-and-span council flats. Russet-cheeked kiddiwinkies are scolded and cosseted by blousy matriarchs married to emotionally reticent beer guts.

The doll’s-house infantilism of Rupert Goold’s production is challenged by designer Bunny Christie whose set is an essay in conceptualism. She uses a vast plastic grid, like an unmade Airfix kit, to suggest the Dagenham car plant. It’s ingenious and intricate but irritating too. Trouble brews at the factory when the executives downgrade the leather workers, who stitch the car seats, to the level of unskilled labour. Everybody out. The strike begins and the show catches fire.

Rita O’Grady, a reluctant Joan of Arc, confronts her bosses at an arbitration meeting. If upholstery is unskilled, she argues, then anyone can do it. Even you. She asks them three easy questions about handling a sewing machine, and their evasive, fumbling answers expose them as arrogant dimwits. Result! It’s a moment of theatrical magic that brings a kick of joy to the heart and a prickle of moisture to the tear ducts. The show never falters after this and it develops into a neo-religious ceremony, a sung Mass extolling the virtues of solidarity and political activism.

Gemma Arterton (Rita) does well in the lead role but she’s more confident as an actor than as a singer. She’s outclassed by two dazzling cameos. Sophie-Louise Dann, as Barbara Castle, invites the female strikers to her gilded Whitehall apartment where she hands out tea like the Duchess of Devonshire, only grander. The role of Harold Wilson becomes a sensational piece of comic theatre in the hands of Mark Hadfield, previously an unremarkable RSC stalwart, who reveals himself as a world-class clown with a Chaplinesque talent for making small physical gestures insanely funny.