Starring: Colin Firth, Matthew MacFadyen, Kelly Macdonald, Penelope Wilton, Johnny Flynn, Jason Isaacs Director: John Madden

WHILE traditional U.S. war films tend to lean hard into valor, sacrifice and vigorous patriotism, the British equivalent more often favors heart and faith, duty and stiff-upper-lip resolve, especially in the country’s rich library of home-front dramas. Audiences with affection for the latter will enjoy John Madden’s “Operation Mincemeat,” a gripping account of an elaborate World War II espionage deception that helped turn the tide for the Allied Forces in Europe. A far more decorous affair than its macho-burger title would suggest, this is a classy production with a first-rate ensemble cast, splicing the story’s intrigue with a poignant vein of melodrama.

The bonus here for fans of quintessentially British spycraft is the presence of a pre-007 Ian Fleming during his time as assistant to Admiral John Godfrey (steely Jason Isaacs), the head of British Naval Intelligence who became the model for the fictional MI5 chief, “M,” in the James Bond novels. Played with martini-dry wit by a debonair Johnny Flynn, Fleming provides the narration and is frequently seen tapping away at a typewriter on what the viewer assumes will form the foundations of his more celebrated career to come.

The stranger-than-fiction case that provides the film’s clunky title is a plan purportedly hatched by Fleming and developed in 1943 by Naval Intelligence officers Ewen Montagu (Colin Firth) and Charles Cholmondeley (Matthew Macfadyen).

Urgency was building for Britain to find a way into occupied Europe, and Churchill (a gruff Simon Russell Beale) had determined that Sicily was the ideal “soft underbelly” to stage the invasion. But given the ease with which the Germans could anticipate that move, a strategic military deception was necessary. The operation aimed to plant documents outlining a falsified planned invasion of Greece on a corpse that would wash up on the coast of Spain, where the information would be intercepted by Nazi spies.

The episode was filmed by Ronald Neame in 1956 as “The Man Who Never Was,” which was based on Montagu’s book of the same name and starred Cliffton Webb and Gloria Grahame.

This absorbingly detailed account was adapted from historian Ben Macintyre’s book (also the subject of a 2010 BBC documentary) by television writer Michelle Ashford, whose credits include “Masters of Sex” and “The Pacific.” Her script balances a methodical retelling of the complex military deception with robust character portraits of the principal figures involved, giving us a rooting interest not just in the warfare maneuvers but also in the personal stakes of those working behind the scenes.

A distinguished barrister at the Old Bailey, Montagu is introduced at a somber moment during a formal dinner that the guests assume is to announce his retirement. In fact, it’s a farewell for his Jewish wife, Iris (Hattie Morahan), and their children, whom Ewen is packing off to America to safeguard against the potential German occupation of England. A strain in the marriage caused by Ewen’s remoteness and his consuming devotion to his work casts doubt over their future reunion.

While brushing off questions from his nosy gadabout brother Ivor (Mark Gatiss), Montagu digs in with MI5’s Twenty Committee, finding a like-minded ally in Cholmondeley, a former RAF pilot whose big feet and bad eyes prompt his self-deprecating identification as “a flightless bird.” Admiral Godfrey is sniffy about their preposterous deception proposal’s chances of success, but Churchill gives it the go-ahead, so they are installed in a basement office and put to work.

Aided by the staunch director of the Admiralty’s secretarial unit, Hester Leggett (Penelope Wilton), they then work against the clock to organize the mission before the body decomposes, synchronizing their efforts with the movements of a submarine sailing from Scotland that would release the body in Spanish coastal waters.

Handsomely shot by Sebastian Blenkov in dark, burnished tones befitting both the era and the secrecy of the plot, this is an agreeably old-fashioned movie elevated by sharp writing, impeccable performances and by a story all the more incredible because it actually happened.

The movie is now being screened in Shenzhen. (SD-Agencies)