MOTHER-DAUGHTER COMEDY TEAM

Together, they constitute a priceless minor comic turn that comes close to stealing a whole film: Phyllida Law and Sophie Thompson as the impoverished mother-daughter tag team, Mrs. and Miss Bates. In a few telling scenes in Douglas McGrath’s adaptation of Jane Austen’s classic 19th century novel “Emma,” they upstage the cast, the crew, even the exquisite surrounding scenery.

Austen calls Miss Bates “a great talker on little matters,” and Thompson plays her to the hilt as a compulsive chatterbox. Miss Bates irritates the genteel, provincial set in which she moves, but no one confronts her; their courtesy and her lowly status forbid it. As the ancient Mrs. Bates, Law cannot get a word in edgewise, but responds mutely to her daughter’s prattle with hilarious, eloquent eye-rolling gestures suggesting horror, disgust--or boredom.

Not that the two women are on screen just for comic relief. In a key scene, the patience of heroine Emma (played by Gwyneth Paltrow) snaps, and she accuses Miss Bates of dullness. The hurt that registers on Thompson’s face transforms her from a figure of fun to an object of real compassion.

The twist is that Law, 63, and Thompson, 33, are mother and daughter in real life. Law has a long, distinguished career as an English stage actress, while Thompson has recently made a name in film (in “Four Weddings and a Funeral”), on TV (in another Austen adaptation, “Persuasion,” made for the BBC but released theatrically in the United States) and on stage (she received an Olivier Award this year for best supporting performance in a musical, the revival of Stephen Sondheim’s “Company”).

While both women have viable careers, they are best known as relatives of a more famous actress: Oscar-winner Emma Thompson, Law’s other daughter and Sophie’s older sister by three years.

Not that Sophie feels overshadowed by her stellar sibling. “We can’t be compared really,” she says, sipping a cranberry juice in an upstairs room at a private London club. “We’ve never done the same sort of work, and we’re never up for the same parts. Which is just as well--it’d be hideous, wouldn’t it? And we don’t even look alike.”

It’s true. Sophie is small and darker than Emma, with thick, wavy, lustrous hair. “No one recognizes me in the street,” she says, “which I like.” But she shares with her sister a deadpan, self-deprecating wit.

Technically “Emma” (the motion picture, not the sister) marks the second time Sophie has worked with her mother. “We appeared together in a sketch for a TV series Em wrote called ‘Thompson,’ ” she recalls. But playing the Bateses was the first real time.

“It was a coincidence we were cast together. [Casting director] Mary Selway had our names on separate lists. In the book, Miss Bates is older than me, and when I first read, Doug thought I wasn’t right. But when I went back, Mary made me let my hair down to look older. And I got glasses, which helped. You’ll see a miraculous change takes place.”

She rummages in her purse, pulls out a pair of small, rimless spectacles and perches them on her nose. “See?” she says. It’s true; she looks 10 years older, and has become Miss Bates in the flesh.

Working with her mother, she says, “was fantastic. You don’t get a chance like that often. We drove down together to and from the set. On one level, you’re working with an actor, and I’d think, ‘Great, I got to work with Phyllida Law.’ Because she’s a wonderful actress. But then I’d drop her off at her house and say ‘ ‘Night, Mum.’ She did make me laugh in our scenes. I had to try and keep her down because I got so hysterical.”

Given her upbringing (her father was the writer and theater director Eric Thompson), one wonders if an acting career was inevitable. “You do wonder,” she sighs. “I pretended I wanted to be a vet for a while, because to say I wanted to act sounded silly and pretentious. It didn’t sound helpful to anyone. But I was in drama groups since I was young, and that’s where I felt at home. Mum and Dad were nurturing to both of us and would have supported whatever we wanted to do.”

She is known in England for a small role as Lydia, the second bride in “Four Weddings and a Funeral.” “I wasn’t married then and didn’t think I ever would be,” she says wryly. “So it was a treat to wear a wedding dress for the film. I got some Polaroids for my grandmother and said, ‘Look, this is how I’d look, if anyone ever asked.’ ” (Recently she did get married, to actor Richard Lumsden who--wouldn’t you know?--is currently filming an adaptation of Austen’s novel “Northanger Abbey.”)

Sophie seems to be cornering the market in comic Austen roles; before Miss Bates, she played Mary Musgrove, best described as one of nature’s party poopers, in “Persuasion.” “But I enjoyed playing Mary because she ate a lot,” she remarks slyly. “I’ve always had an aversion to people who eat a bit of lettuce and that’s the end of the meal. So I think it makes me a good role model to play someone who enjoys their food.”

Nor does she agree that there is a surfeit of costume drama on film and TV. “Not at all,” she says defiantly. “I like wearing bonnets. And I do like an Empire line. People cut a fine dash in them. Oh yes, it’s lovely getting into a costume.” If you are alert, you catch her darting, sideways glance as she checks out how seriously her listener is taking all this.