For a newcomer to the celebrity circuit, Cathy Tyson certainly knows how to make an entrance. Forty minutes late for her dinner interview at a Manhattan restaurant, she arrives by limo with her husband, Craig Charles. Heads turn as they bound toward the garden. Dismissing the formal dress code, Tyson wears a revealing low-backed dress. But even so, she is upstaged by Charles, who sports a flowing green-and-white-striped outfit that looks like pajamas. Finding the floral arrangement on the table bothersome, Charles banishes the bouquet to the floor for an unobstructed view of his beloved. Tyson responds with secret gestures that seem to be in the sign language of Aphrodite.

Britain's Cathy Tyson, 21, has been making lots of startling appearances. Her film debut in the critical smash Mona Lisa is one of the year's most heralded performances. Playing an elegant black prostitute who becomes the love object of Bob Hoskins, Tyson reduced even the New York Times to mash notes: She "has a magical screen personality...beautiful, intelligent and hard as nails." Whether her character, Simone, is having an assignation in London's pricey hotels or being driven through seamy back streets, Tyson is a portrait of beauty, as enigmatic as the painting in the title.

Offscreen, however, Tyson displays none of the icy sophistication that colors her performance. For refreshment, she orders a "wet willie" (the British equivalent of a Shirley Temple). In conversation she gives in to the harsh accents of her hometown, Liverpool. So why did director Neil Jordan choose this antithesis of chic over the many actresses who sought the part of Simone? "He said he wanted someone young and virginal," says Tyson. Says her husband: "Ooo, I like that virginal bit, girl."

Tyson did no background preparation for her role as the high-class hooker. Instead, "I just took the script into the kitchen and read it while I did the dishes," she says. Contemptuous of method acting—"You don't have to be a junkie to play one"—she never considered talking to prostitutes for research. "Maybe some actresses feel they need to talk with them because they feel far removed from the world. I don't," she says pointedly. Her single concession was a one-hour lesson in how to walk in high heels. "I'm a bit floppy at home, and I'm always barefoot. Swiveling is very important to Simone. I had to learn to make it look Dynasty-esque."

Tyson's background is far removed from the world of Mona Lisa. An only child (her father was a black barrister from Trinidad, her English mother a white social worker), she was raised by her mother after her parents' divorce. "I grew up in a working-class world, but we never starved," says Tyson, who shuns discussions of her parents and their interracial marriage. Self-reliant and spirited at an early age, she dropped out of college at 17 and, despite her lack of any formal training, was soon performing at Liverpool's Everyman's Theater. Seen in a 1984 production of The Blitz Show there, she was asked to audition for the august Royal Shakespeare Company. At the tryout, she played the part of the innocent Miranda in The Tempest, and her reception was chilly. "I read in front of five intimidating directors, and when I finished, someone in a very snobby voice said, 'How come you're doing a Liverpool accent? Where is your BBC English?" Ever unpredictable, Tyson replied, "Listen, luv, I know I'm not just doing this for my own backyard. I know how to speak proper English as well. I just thought interpretation was more important than the way you speak." She won admission to the company, but then suffered through the typical apprenticeship of sweeping stages and carrying spears in Julius Caesar. Ironically, however, Tyson has found life at the RSC more eclectic than she expected. "There are all sorts of accents now," she says. "Being at the RSC is like spending a Saturday afternoon at a fish market." She is currently playing a mistress in an RSC production of Mephisto.

Like her career, her love life had its beginnings in Liverpool. She met Charles, then a 19-year-old performance poet, when she heard him speak at a local theater three years ago. After she asked him for an autograph, he asked her for a date. They married in 1984 and now live in a one-bedroom London flat, which they share with cats Tillie and Caspar. ("He's named after Caspar Weinberger," Charles explains. "He's a fascist cat that eats everybody's food.") In England, where Mona Lisa has not yet been released, Charles is the famous name. He's a regular on the satirical Saturday Live TV series, and his poetry readings frequently take him far from home. "I'd rather drive 500 miles in my van than sleep away from her," he says. "She's sexually exciting." Charles thinks they are bonded in part by their common background: "We both come from Liverpool, one of the poorest cities in Europe, so everything we get is a bonus."

After dinner Tyson inadvertently finds herself in the midst of a scene straight out of Mona Lisa. As the limo traverses Times Square, Charles opens the sunroof for a better look at the ladies of the evening. For a split second, Tyson assumes the impervious, imperial demeanor of her screen alter ego, Simone. Without turning to consider the sidewalk sights, she observes, "They're busy earning their livings, for God's sake." In her idiosyncratic fashion, so is Cathy Tyson.