Dramatic fireworks begin when Ben Barnes as John Whittaker brings home his new bride, Jessica Biel as Larita, a flamboyant and stunning American racing car driver with a hidden past. He is in no way equipped to handle such a woman, but he has been smitten by her, and she by his innocence. He’s a mama’s boy, and mama, Mrs. Whittaker, as played Kristin Scott Thomas, immediately dislikes her new daughter-in-law, who is a threat to her plans to have John take over the financially pressed estate.

On her part, Larita can’t stand the stuffiness she encounters, and after trying to fit in, rebels in mischievous ways that flaunt the local traditions. She and Mrs. Whittaker are at constant loggerheads and much of the battling is hilarious. Thomas plays the ogre very well, but fine actress that she is, also manages to inject some poignancy when she reveals the desperate economic situation she faces. There is also a back story of how she went searching for her straying husband, Jim, disillusioned by the horrors of serving in World War I and burying his anguish in alcohol. But he finally came home to her.

Jim, played superbly by Colin Firth, has become obviously remote and is fed up with his wife, their two boring daughters and the lives they lead. Instead of disliking Larita, he finds her entrance into the household refreshing. Biel is a delight in the role. She looks great, and has a commanding presence that enlists one on her side.

The screenplay, by Stephen Elliott, who directed, and Sheridan Jobbins, is rich in Coward-style wit, complemented by the picture-perfect period costuming and striking location settings making use of British stately homes as stand-ins. As director, Elliott, best known for his “The Adventures of Priscilla Queen of the Desert,” keeps the film light-hearted in style even while jabbing pointedly at the society under inspection. It also moves quickly. Some scenes are laugh-aloud funny, especially one involving the pet dog of Mrs. Whittaker. You also may along the way forecast the ending.