“I think Sally Rooney had a similar feeling to me, which was like, ‘I can’t believe this is happening,’ ” says Daisy Edgar-Jones. At a smart café in North London, the 21-year-old actor is discussing—and, it seems, still processing— her star billing in the BBC and Hulu adaptation of Rooney’s best-selling novel Normal People. “When we were making it, we didn’t even register that people were actually going to see it,” she says, settling into a sunny window seat.

In the nearly two years since its publication, Normal People has generated a fandom with the passion of Potterheads, Trekkies, or Marvelites—only with more New Yorker tote bags. The novel tells the story of a turbulent love affair between the rich, smart Marianne (played in the adaptation by Edgar-Jones) and the equally smart but workingclass Connell (played by the 24-year-old Irish actor Paul Mescal), whose relationship begins at school in small-town Ireland and intensifies in both its passion and its heart-wrenching complications at Trinity College in Dublin.

Neither actor had read the book before auditions were set, but a surprising number of people had told Mescal he was a perfect fit for the part of Connell, he recalls when we speak over the phone during a break in rehearsals for a revival of The Lieutenant of Inishmore at Dublin’s Gaiety Theatre. Mescal grew up in Maynooth, a town just west of Dublin. Like the onscreen Connell, he spent his school days playing Gaelic football, and like Connell he moved away from his small hometown to study at Trinity—he got his drama degree at the affiliated Lir Academy in 2017.

Edgar-Jones, on the other hand, had never even been to Dublin when she was called to audition in March of last year. An only child raised in London’s Muswell Hill neighborhood, she grew up on the periphery of the entertainment industry, her mother a film editor from Northern Ireland, her father a Scottish TV producer who ran the groundbreaking reality show Big Brother. Although she acted with the National Youth Theatre as a teen, she never attended drama school or university, and got her first part—a small recurring role in the British comedy-drama series Cold Feet—while still at school. “I came in kind of like Marianne—a bit of an outsider,” she says. While Mescal is a theater veteran, having starred in several high-profile Dublin productions, Edgar-Jones is only now taking on her first professional play. She’s spent the morning in rehearsals for the Almeida Theatre’s production of Albion, a state-of-the-nation drama about England’s chronic nostalgia for a grander past. For Lenny Abrahamson, who directed Normal People along with Hettie Macdonald, the casting process was all about finding “the right pair.”

On the phone from Dublin, he tells me that while they had Mescal penciled in for Connell within days, finding Marianne took months. “Close to when we were beginning to get really worried, along came Daisy,” he recalls. Once the two actors were in the same room, Abrahamson became aware of an “ineffable” chemistry between them. “It’s not unlike what draws people together in life,” he says. “You can feel this amazing spark.” Both actors recount that the five months of filming were extraordinarily intense. “It cost a lot,” says Mescal, “in terms of energy and time and what you can give to other people.”

Rooney’s descriptions of intimacy in Normal People are startlingly unvarnished, and its directors remained faithful to that spirit, meaning Edgar-Jones and Mescal spent more time naked together during filming than some real-world couples might over the same period. Both had partners at the time (although Mescal and his girlfriend have since broken up), and Edgar-Jones insists that the fact they were simply “great friends” made the sex scenes easier to manage. “I think if I had to do those scenes with Tom,” she says, referring to her boyfriend, the actor Tom Varey, “I would probably have been completely self-conscious.”

Mescal compares the role of an on-set intimacy coordinator to that of a stunt coach: “I can’t imagine doing a show like Normal People without one.” Before Normal People took off, Edgar-Jones was studying for an Open University degree, and she’s clearly someone drawn toward schemes for self-improvement. A non-exhaustive list of current activities includes reading (most recently Ann Patchett’s The Dutch House), visiting art exhibitions, and doing daily yoga videos. For Mescal, time spent not working is a bit more of a puzzle. He reluctantly gave up Gaelic football after a broken jaw during drama school taught him the two passions “don’t coexist, unfortunately.”

Although he dabbles in photography and plays the piano, he has yet to find a hobby that can fill the sizable void left by competitive sport. “I’m figuring that I’m not good in the downtime,” he says. But a new start beckons: He’ll be spending more time in London in the coming months.“Professionally, I think it’ll be maybe the right time to be over there,” he explains.

In London, living only a few miles from each other, the two actors will wait and see whether Normal People will elevate their lives to something far from ordinary. Is Edgar-Jones ready for the sort of fame where you deliberately don’t choose to eat lunch in a huge, street-facing window, as she has done today? “I’d probably find that a wee bit odd,” she says, smiling.