Dev Patel, Starry Knight

Horses know, Dev Patel told me.

“A horse can tell if you’ve only slept two hours the night before,” he said. “If you’re anxious, the horse can feel it. Armani definitely could.”

Armani is one of Patel’s most significant co-stars in the new medieval fantasy “The Green Knight,” in which the 31-year-old actor plays Sir Gawain, a would-be warrior who embarks on something of a suicide mission. Parts of his quest take place on horseback and Patel, who’d never ridden before, tried to win Armani’s favor by sneaking him apples pilfered from the hotel lobby in Dublin.

Still, appealing to a horse’s stomach can only do so much. If Patel couldn’t summon enough leading-man authority to embody Gawain, surely Armani would be the first to sense it. After all, they would spend their first shoot day together in an Irish wilderness where the wind blows so strong that Patel found himself gripping Armani tightly just to stay upright.

As those gusts of cold air pierced the metal mesh of Patel’s chain mail in a way no sword could, did Armani know that his rider was more neophyte than knight? And could the horse sense some of the other things making Patel anxious, like his natural tendency to overthink his career — what Patel calls “paralysis by analysis” — or the way he wondered what people would make of a British-Indian actor playing King Arthur’s nephew?

OK, maybe some of those concepts are a little too complicated for a horse to suss out. (Though Armani could not be reached for comment, so who’s to say?) But Patel still had a lot on his mind that first day, and I haven’t even gotten to the matter of his food poisoning yet.

“All this talk of representation,” he groaned, “and I’m here on top of a horse in chain mail, in the freezing cold, hoping I don’t get diarrhea.’”

Patel was video-chatting with me from Adelaide, South Australia, where he’s busy editing his directorial debut, a martial-arts movie called “Monkey Man,” as well as keeping an eye on the “The Green Knight,” which was originally meant to come out last summer and will now debut in theaters on July 30. Directed by David Lowery, “The Green Knight” adds a welcome swerve to Patel’s résumé of straightforward crowd-pleasers: Unlike “Slumdog Millionaire” or “The Best Exotic Marigold Hotel,” Lowery’s film is artsy, mysterious and a little sexy.

Or, let me put it more plainly: “The Green Knight” understands that Dev Patel is a heartthrob now.

The once-gawky actor has grown into a leading man with romance-novel hair, empathetic eyes and a well-kept beard, and though photo shoots of Patel routinely earn big numbers on social media, no movie till this one has really capitalized on his status as an internet crush. Patel wasn’t even on Lowery’s initial casting list for “The Green Knight,” but after the director saw a Zegna fashion spread with Patel looking suave and regal, he found himself so taken with Patel’s potential that he started drawing a picture of the actor on horseback.

“From the moment I met him, I was very aware that he was going to be the thing that makes the film epic,” Lowery said. “If we couldn’t move to an epic location, if we weren’t able to find the right vista, I could always fall back on him because he will give us that in a close-up.”

Sir Gawain is a bit of a cad when we first meet him, a drunken layabout who’d rather woo than fight. Still, he feels that it’s his destiny to be known for something great, and when a treelike creature called the Green Knight issues a challenge to King Arthur’s court, Gawain too eagerly accepts, beheading the monstrous figure.

Unfortunately, the Green Knight survives his own decapitation and promises to return the blow to Gawain in one year’s time. This means that though Patel is introduced as a romantic rogue — and Lowery steers into that idea, outfitting him in a series of low-cut blouses — it’s the rest of the movie, in which Gawain finds himself humbled by the Green Knight’s looming deadline, that is truly meant to test his mettle as a man.

“I’m certainly aware of all of the fans of Dev Patel’s hair and beard — I’ve seen those memes,” Lowery said. “But I don’t think people understand exactly what he’s going to be doing as an actor and ‘The Green Knight’ just scratches the surface of it.”

Lowery’s film is enigmatic enough to mean different things to different viewers, and it’s sure to spawn a thousand subreddits devoted to decoding its dreamlike logic. But to Patel, the main point of “The Green Knight” is clear: Gawain thinks he is entitled to fame even when he has done nothing to prove it’s deserved. His quest, then, is a journey toward integrity that comes with some present-day parallels.

“Whether you’re an Instagram model or a YouTuber, there’s this thirst to be recognized, to have your legend spoken about, to get the likes,” Patel said. “And for me as a young actor in Hollywood, you’re dealing with issues of masculinity, ego, success and fame. That’s the same quest this young man goes on to be a known knight. All of that, I related to.”

NONE OF THIS was originally in the cards for Patel, who grew up in the London borough of Harrow as the younger of two children. Both his parents had emigrated from Nairobi in their teens. His father, Raju, is quiet and introverted, while his mother, Anita, is the family’s force of nature. “She’s a big personality, and she can have the whole room laughing,” Patel told me. “I think my love of playing all these characters came from her.”

Patel was a hyperactive child, and his parents signed him up for years of martial-arts classes to channel that excess energy. Still, he always had something more to give, and when his mother saw a casting advertisement for “Skins,” a teen drama that would supercharge the careers of young actors like Nicholas Hoult and Daniel Kaluuya, she prodded him to audition for the role of sex-crazy Anwar.

The show was a hit, but the neighbors were horrified. “It felt like suicide in the community to put your kid into a TV show and let him drop out of school at 16,” Patel said. “While everyone else’s kid is off becoming a doctor or a dentist, I’m here on this TV show,” he said, “simulating sex and taking drugs.”

He had never acted on camera before, and “Skins” was a trial by fire. The money was good enough to improve his family’s situation — with his first paycheck, Patel bought his sister a new bed — but the show’s large online following cut both ways.

“I was a young kid going on these chat rooms and it was quite brutal,” Patel said. “There were all these lists of who’s the favorite character on the show or who was the best-looking character, and I was always the ugliest, the least attractive. No one liked Anwar. It really took a toll on me personally.”

Maybe that’s why he still mistrusts compliments 15 years later, or why he makes fun of himself before anyone else might get the chance. When I bring up the fan base that’s rooting for him on social media, I can’t even finish the sentence before Patel interjects: “All three members of that fan base?” Even when “Slumdog Millionaire” won best picture at the Oscars in 2009 or when, eight years later, Patel himself received a supporting-actor nomination for the drama “Lion” (he lost to Mahershala Ali), all that attention made him uneasy.

“I didn’t feel worthy,” he said. “That kind of speaks to my natural low self-esteem: You’re there with really impressive creatures, the best of the best, and you’re like, ‘I don’t know what I have to offer in this space.’”

He said his agents still get frustrated with him for turning down major studio blockbusters. “Maybe it’s a fear of how I would fit into that world,” Patel said. Sheepishly, he begins to talk about “one of the worst movies I’ve ever done, and I shouldn’t even bring it up, but do a quick IMDb search and you’ll know what it is.” (He’s referring to M. Night Shyamalan’s “The Last Airbender,” the Razzie-winning adaptation of the animated action series.)

On that production, he was surrounded by green screen and special effects, and the artifice proved too difficult to wrap his head around. “I didn’t really flourish in that position,” he said. “I take my hat off to all those incredible actors that do Marvel movies where it’s, like, big, noisy fans and green screen and tennis balls and whatnot.”

Authenticity is Patel’s watchword; if he can’t make a movie feel real to him, it’s not worth doing. By way of explaining, Patel told me a story about landing the role of the teenage striver in “Slumdog Millionaire,” an audition he booked because the daughter of the director, Danny Boyle, was such a fan of “Skins.”

Patel was full of manic energy during the audition, using every trick he could think of to earn laughs in the room. But afterward, Boyle took the young actor aside and told him that if he were hired to lead the movie, he’d have to learn to be still. Could he leave enough room for the audience to enter the film through his eyes?

“At the time, I was 17,” Patel said, “and I was like, ‘Well, that’s not acting. That’s just lazy!’” But over the course of his career, he has begun to understand what Boyle meant: All you really have to do is be present. A movie star knows that’s enough.

That’s why the most exciting thing for Patel now is when he plays a role that lets him simply be. With its long, meditative scenes set in real locations, “The Green Knight” delivered that feeling in spades: Even when he was astride Armani and the rain hurled by the wind felt like bullets hitting his skin, Patel wouldn’t have traded the truth of that moment for anything. It’s the reason he does what he does, when all that’s left is him, the camera, and something powerful and innate that commands attention. (Horses can sense that sort of thing. Maybe audiences can, too.)

“There’s a moment between ‘action’ and ‘cut’ that is like a drug,” Patel told me. “If you’re with the right filmmaker on the right set with the right script, everything just dissolves away.” He likened it to the flow state reached by great athletes, or even to Kate Winslet on the prow of the Titanic: “And there’s a metaphorical DiCaprio behind me,” he said, extending his long arms and grinning.