MODERN LOVE Matthew MacFadyen doesn't always wear frock coats; he's also a spy guy from A&E's "MI5".

To play Mr. Darcy, literature's most desirable bachelor, actor Matthew MacFadyen knew he had some extremely tight breeches to fill. Every Austen fan the world over has already chosen his or her ideal embodiment of the rich, taciturn brooder who fascinates Pride & Prejudice's heroine, Elizabeth Bennet. For many, that mantle belongs to Colin Firth, the leading man in the 1995 BBC/A&E adaptation, who secured his place in television history with a decidedly not-in-the-book moment when Darcy removes his frock coat and goes for an impromptu swim. MacFadyen gives props to Firth: "In Britain, his wet-shirt leap out of the lake scene is on every Christmas as one of the 100 best moments in TV, and it's superb."

MacFadyen, who's best known to U.S. audiences as lethal but loyal Brit spy Tom Quinn on the A&E series MI-5 and for numerous PBS dramas (The Way We Live Now, Perfect Strangers), further upset Austenites when he casually admitted that he had never read the novel. "One journalist got really snotty," says the 30-year-old Brit, who orders beer, not tea, in a Toronto restaurant. "She gave me a big lecture and said I had no respect for Jane. The truth is, you rehearse with a script, actors and your director, not a book. That's how you discover the character. Darcy's unpracticed and awkward. He's still grieving for his parents. His first big test in looking after his younger sister, he fails." MacFadyen has since read the novel, which he describes as "gorgeous, comforting, robust," but still feels he did right to work from the screenplay: "A good script will lead you on the right path."

Pride's director, Joe Wright, 33, was determined to cast performers of the correct age. "Elizabeth and Darcy, who are 19 and about 30, have never been in love before. Fancies, perhaps," Wright says. "Hire actors older than that and it becomes embarrassing." The 1940 film adaptation had Greer Garson and Laurence Olivier, both in their mid-thirties, "carrying on like teenagers," he says, while the 1995 miniseries had "intelligent actors, polished performances, but I personally did not believe it was a first-time romance."

The director was immediately struck by MacFadyen's "integrity, his sense of honor, the vulnerability in his eyes." He adds, "Matthew's a big bloke, a manly man. Until Lizzie encounters Darcy, she's fancied pretty boys. But Darcy intrigues and frightens her a little. You need an intimidating actor to do that, because Lizzie's such a forceful woman."

Though Wright makes note of MacFadyen's distinctive pale blue eyes, the film contains several unusual reaction shots—not of the hero's face, but of Darcy's hands, the only other flesh that's exposed by the period costumes. "I did find myself clenching my hands quite often," MacFadyen says. "I had this secret: I thought that in Darcy's encounters with Lizzie, whenever she gets at him, really hits him with a sort of verbal body blow, he couldn't react right then. He'd have to go back home, shut the door to his bedroom, lock it, and collapse with laughter at himself. He'd be totally infuriated. But it would tickle him so much. That's why Lizzie is so attractive."

In real life, MacFadyen's got his own ideal romance: He's married to actress Keeley Hawes, his costar from MI-5. Their next assignment is to take a holiday trip to Mauritius, where he'll read re-views "with fear and delight." The actor savors one early notice from a critic who compared his Mr. Darcy to a "droopy cartoon dog." (Major critics have been generally favorable, otherwise.) "My favorite interview question is, 'How will you make your Mr. Darcy different?' which is not well thought out, I think. I want to say, 'I'm going to play him gay! He's not interested in Elizabeth at all.' No: 'I'm going to play Darcy as a blind man. I'm going to play him as a droopy cartoon dog,' which won't be difficult, because that's what I look like!" Then he laughs, which is something that Mr. Darcy would never do. At least not in public.

Pride & Prejudice opens in theaters Friday 11.