Dev Patel, Starry Knight

“The Green Knight” offered the actor a movie-star moment unlike anything he’s done before. Could he conquer his insecurities and take the lead?

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 takes 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.