Though firmly founded in the bubbly screwball comedies of the 1930s, this London-set period comedy has the power of hindsight, and thus edges its pleasures with the poignant awareness of impending war. There’s an explicit gap of understanding between those characters who remember the Great War in detail – like Frances McDormand’s fussy spinster Guinevere Pettigrew – and the younger individuals around them who still consider air-raids and blackouts a bit of a laugh.

Guinevere, a severe but vulnerable amalgam of Mary Poppins and Virginia Woolf, is out of work as a domestic, largely because she keeps passing terrible judgement on the people she serves and attempting to change their ways. In financial desperation, she cons her way into an agency job intended for someone else – and meets the irrepressible, capricious actress Delysia Lafosse (Amy Adams), who juggles outrageous fantasies of stardom as well as three competing boyfriends. Adams, celebrated for her wide-eyed turns in Junebug and Enchanted, is smart enough to play Delysia not as a Carole Lombard clone, but as an ordinary, movie-crazy girl who has practiced very hard to be a Carole Lombard clone.

McDormand, meanwhile, kicks Guinevere off as an entertainingly flat-footed spoilsport, but gradually permits her humour, wisdom and endearing sense of wonder to show through. With the Blitz on its way, Miss Pettigrew’s life-changing makeover at the hands of society stylist Edythe Dubarry (a perfectly icy Shirley Henderson) seems to have less to do with vanity than with grasping at luxury while it’s still possible – and her stern management of Delysia’s love life indicates a corresponding urge to secure small moral victories ahead of large-scale tragedy. The film’s bubble baths, fashion salons and rat-tat-tat exchanges, meanwhile, are pure Old Hollywood (even if Delysia’s claim to have appeared in A. Edward Sutherland’s Every Day’s A Holiday – “in the restaurant scene, behind a palm tree, drinking a margarita” – doesn’t quite ring true).