Starring Gemma Arterton. Rated 14A

The title here is truncated from novelist Lissa Evans’s Their Finest Hour and a Half, a cheeky reference to a famous Winston Churchill speech made just before the Battle of Britain. In late 1940, France is already lost, the U.S. has not yet entered the war, and the demand for morale-boosting entertainment—an uplifting 90 minutes, let’s say—is at an all-time high.

Demand is also surging for the professional services of women, which is how Catrin Cole (a delightful Gemma Arterton), a Welsh transplant to blitz-blighted London, managed to turn copywriting experience into a job with the Ministry of Information. “We can’t pay you as much as the chaps, of course,” explains her cheerful new boss (Richard E. Grant). What she thinks is a secretarial gig turns out to be working on a script for a new propaganda film.

Upon realizing that the story she’s been given to work with, about twin sisters stealing their dad’s boat to help rescue soldiers from Dunkirk, was largely fabricated by local newspapers, she weaves some flannel of her own. She needs the dosh to support her moody husband (Jack Huston)—a painter wounded in the Spanish Civil War—and enjoys the screenwriting camaraderie with a sleepy older fellow (Paul Ritter) and the crankier Buckley. Younger viewers will recognize the latter, beneath his glasses, ’stache, and Brylcreem, as Hunger Games dreamboat Sam Claflin.

Their work is intended to boost morale and help invite Yanks aboard, as explained by their Alexander Korda–ish producer (Henry Goodman) and a stuffy cabinet minister (Jeremy Irons, in a great cameo). The movie we’re watching, then, is a boon to lovers of British cinema, with the bonus of comic opportunities handed to Bill Nighy, as an aging ham actor whose flagging career could be revived by this home-front codswallop.

As assembled by An Education director Lone Scherfig and veteran TV writer Gaby Chiappe, all the parts here work together beautifully. It’s a shame, then, when the incipient romance between Buckley and Catrin moves to the foreground, breaking the collective momentum of the story and flow of her self-discovery. Their Finest recovers, however, and these two hours are quite rewarding.