On a recent morning in London, British actor Emma D’Arcy was dealing with “an emergency.”

D’Arcy was in a studio, rerecording voiceover as Rhaenyra Targaryen for the second season of HBO’s hit “Game of Thrones” prequel, “House of the Dragon.” It was the fourth time the actor, who uses they and them pronouns, had recorded this particular bit of dialogue, and each time they were confronted by an enormous screen showing their face, surrounded by unfinished special effects.

It was like a rather brutal “Groundhog Day,” they said, adding wryly that “the process of repression happens very quickly when you’ve got a job to do.”

As the breakout star of “House of the Dragon,” which recently returned for its second season on HBO, D’Arcy, 31, has had to adjust to seeing their image blown up. “Emma is literally the face on the poster,” Ryan Condal, a “Dragon” creator and showrunner, said in a phone interview, adding that he couldn’t imagine what it must be like “taking that on but also still being an artist and a serious student of the craft.”

D’Arcy has been grappling with this tension since “Dragon” first aired in 2022, when it became the most watched premiere in HBO’s history. Set approximately 200 years before “Game of Thrones,” the show centers on the Targaryen dynasty before its dramatic fall. D’Arcy’s headstrong dragon rider, Rhaenyra, who must defend her claim to the Iron Throne, quickly emerged as a fan favorite.

In the second eight- episode season, D’Arcy is in every episode, whereas in the first 10-episode season, Milly Alcock played a younger version of Rhaenyra in six.

“What I realized retrospectively is, four episodes — mwah!” D’Arcy said, miming a chef’s kiss.

The second season was more emotionally difficult, too. At the end of Season 1, Rhaenyra’s son Luke is killed by a dragon, and so D’Arcy’s character is “stricken with grief,” they said. “She’s made an island by her loss,” radiating “a violent, vile feeling — like a hatred feeling.”

Shortly before shooting on the second season started, D’Arcy said they had also grieved a major loss in their own family.

“It was a weird time to be invited to meditate on grief in one’s work, while trying to find some space to put one’s actual grief,” they said quietly. Like Rhaenyra, they said they were angry.

Matt Smith, who plays Rhaenyra’s uncle-turned-husband, Daemon, said in a phone interview that D’Arcy had “an ability to be in one’s tragic self, quite openly.” As an artist, D’Arcy’s focus was “forensic, and driven by a laser intellect,” he added.

Growing up in a suburb of Gloucestershire, in southwest England, D’Arcy’s parents encouraged artistic expression, the actor said. Their mother had been an illustrator before D’Arcy was born, and while their father’s day job was in security, he was “an obsessive painter and photographer,” they said.

As a child, D’Arcy watched a VHS tape of “Joseph and the Amazing Technicolor Dreamcoat” and became “completely obsessed” with the musical’s narrator, who had short blond hair and wore a long trench coat. “That character is in charge and had this androgynous appearance,” D’Arcy said. “I thought, ‘I would like to be like you.’ ”

After a “pretty unpleasant” experience at high school, D’Arcy spent a year studying art, specializing in sculpture. “For me, it was like fireworks in the brain,” they said. They went on to study Fine Art at the Ruskin School of Art, part of Oxford University, and spent their early 20s co-running a theater company, directing and designing sets alongside acting.

“I’d been growing my hair out to look more feminine because I thought that would help me get an agent,” D’Arcy said. But when they got one, in 2016, the actor had what they described as “a total panic” and wondered if they would have to choose between acting work and living in a way that felt authentic to their gender identity. In 2020, when HBO asked D’Arcy to confirm their pronouns before filming “House of the Dragon,” they realized they wouldn’t have to make that choice.

Before they took on the role of Rhaenyra, D’Arcy wrote a list of pros and cons to taking the job. They auditioned during the pandemic and had just lost a year’s worth of work. On the pros column, “There was just like, ‘prospect?’ written,” D’Arcy said, laughing, as well as “ ‘might have to grovel less to get work?’ ”

Becoming recognizable was on the con side. But D’Arcy felt confident that “if you stop being on telly, it goes away.” Since the show’s first season aired, they have still been able to cycle around London and have “a completely normal time,” they said, partly thanks to the wig they wear as Rhaenyra, which is waist-length and platinum blond.

“I owe it a huge debt of gratitude,” D’Arcy said dryly, running a hand through their short, tousled brown hair.

D’Arcy said they weren’t always comfortable being treated as the talent, even on the “House of the Dragon” set, where their name is at the top of the call sheet and they have their own makeup tent.

“I found the set hierarchies particularly difficult to make sense of,” they said, adding that it was different from the all-hands-on-deck approach they had become used to while running a theater company.

In 2022, D’Arcy suddenly got a lot more attention after a video went viral of them explaining their favorite drink — “a Negroni … Sbagliato … with prosecco in it” — to their “Dragon” co-star Olivia Cooke. It “still seems like something that happened to someone else,” D’Arcy said.

D’Arcy’s vocal delivery in that clip — arch, but with an air of James Bond suave — turned them into a meme. In a phone interview, Cooke described D’Arcy’s voice as “earthy and resonant” and “quite sensual, in a way,” adding that she “could listen to them read the ingredients on a cereal box.” Cooke stifled a giggle. “Oh God, I sound weird, like one of their fans,” she said — although, she added, “I am one of their fans!”

D’Arcy said that recently, they had been invited to play more characters on the masculine end of the gender spectrum. “The hope is that there are more of those roles floating around,” they said. Still, it had been a long time since they had been on screen wearing a pair of pants, situated in the modern day.

“I’d love to be here,” they said. “I’m ready to be in the present.”