The British actor Jeanna de Waal is obviously not the first person to play the part of Diana, Princess of Wales, or even the first person to do it this year. “When we started, it was a lot less populated, the pool of people who played her,” said de Waal, who stars as the title character in “Diana, the Musical,” which opens on Wednesday after a long pandemic delay.She is not disconcerted by the Diana-Industrial Complex. “I watch them all, and I can see what they’re doing,” she continued, speaking of the other Dianas in circulation — currently, Emma Corrin in “The Crown” and Kristen Stewart in “Spencer” (there’s also Diana herself, who appears in the CNN documentary series “Diana”). “What I mean is, we all got the same homework, and we all have the same sources, but we all do it differently,” de Waal said. “There are two million ways you could tell her story.”“Diana, the Musical” tells it in song. The tale of Diana’s ill-fated marriage to Prince Charles, the heir to the British throne, the production is a frothy, peppy, archly exuberant trip through the familiar byways of this tragic royal relationship, from the couple’s blundering courtship to the recrimination-filled conclusion of their marriage. (There’s a sad coda at the end, foreshadowing Diana’s doomed future.)Roe Hartrampf, center left, as Prince Charles and Jeanna de Waal as Diana in the musical, which is in previews at the Longacre Theater.Sara Krulwich/The New York TimesIt’s been a long road to Broadway, and de Waal has been there for all of it, since the production’s first workshop, at Vassar College, in Poughkeepsie, N.Y., back in 2017. The musical opened at La Jolla Playhouse in 2019, moved to Broadway the following year, and shut down after nine previews in March 2020. The set was locked up at the Longacre Theater; the cast and crew scattered.In person, de Waal, 33, doesn’t immediately evoke Diana. For one thing, she dyed her dirty-blond hair dark during lockdown, and has kept it that way since. (She wears a series of increasingly dramatic Diana wigs for the show.) She is also forthright and un-self-conscious in a way that Diana, who always seemed brittle beneath the glitter, never was.De Waal is onstage for almost the whole musical, portraying a sheltered, unworldly young woman whose hidden gifts — charisma, sex appeal, a knack for publicity, an extraordinary common touch — turn her into a global celebrity and a stealth influencer. “Sometimes, though, it’s best,” she sings, “to be underestimated.”“What we have now is a much more juicy and titillating story of what this marriage was,” de Waal said.Josefina Santos for The New York TimesIn taking on the part, de Waal has had to contend not just with all the other dramatic Dianas, but also with legions of opinionated Diana fans who bring their own preconceptions to new depictions of her. Then there is the problem of lowered expectations. In October, a version of the musical, filmed in an empty theater late last year, was released on Netflix. The response, to put it mildly, was very bad.The New York Post called it “the flop of the year.” The Guardian gave it one star and said it was “a Rocky Horror Picture Show of cluelessness and misjudged Judy Garlandification.”On Twitter, mesmerized viewers seemed to be hate-watching the show as they would a terrible camp classic. “I’m so sorry but the Diana musical might be the best worst musical ever written,” one viewer tweeted.The good-natured de Waal responds to questions about this awkward situation with what appears to be constitutional equanimity. (“She’s so centered,” is how the musical’s director, Christopher Ashley, put it.) Even as the mean tweets came in, her direct messages were filled with enthusiastic responses from people who loved the musical, she said. In addition, the broadcast got people talking, she said, and put the production on lists of shows to watch on Broadway.“Look, we didn’t film this for Netflix because we thought it was bad,” she said. “We thought it was fantastic.”Ashley said in an interview that the production had made numerous changes since filming the Netflix special. The theater’s emptiness — the lack of laughter, of applause, of an audience’s ineffable energy — drained the production of its high-octane metabolism, he said. “Having an audience changes what it feels like.” From left, de Waal, Hartrampf and Erin Davie (as Camilla Parker Bowles) in what de Waal calls, “the story of a woman’s revenge.” Sara Krulwich/The New York TimesEarly Broadway audiences appear not to have heard, or not to care, about the unfortunate publicity. At a preview the other night, the theater was filled with Diana-philes eager to bask once more in a story they know so well. They wore “Diana” face masks; they applauded the cunningly staged, lightning-quick royal costume changes; they queued to buy mugs, hoodies and other merchandise. There was applause for iconic outfits; gasps at the appearance of the princess’s love rival, Camilla Parker Bowles; and a standing ovation at the end. In the line for the bathroom, women debated the relative evilness of Charles and Camilla.The producers always promised that the show would make it to Broadway after the pandemic. But they had no idea what that would entail. “I remember the phrase ‘flattening the curve,’” Ashley said, referring to the city’s coronavirus lockdown. “We thought it would be for a few weeks. The possibility that it would be 600 days before we were back in production on Broadway — that was something we didn’t plan for.”As the days without pay stretched on, the cast and crew had to find other sources of income. For de Waal, that came from running Broadway Weekends at Home, a remote version of the musical theater camp that she founded with her sister, Dani, a former actor who works for Google. Hundreds of people signed up during the pandemic, paying a subscription fee to be taught by Broadway and West End performers.Born in Germany and raised in England, De Waal was always obsessed with musical theater. “I became a fanatic,” she said. “For birthdays and Christmases, I would ask for CDs of original cast recordings.” After earning a degree at the Liverpool Institute for Performing Arts, she got a job in the ensemble of, and as an understudy in, “We Will Rock You” on the West End. “It was a baptism of fire,” she said. “I had never done any mic technique work. You know that old thing where singers just sang really loud? You don’t need to do that with a mic. I bought a microphone, and I practiced at home.”In the late aughts, she moved to New York. “I had no agent, no job, and I started doing Times Square open calls,” she said. “I knew no one, and I felt very grown-up and free.” But soon the work was rolling in: parts in “American Idiot,” “Carrie,” the “Wicked” national tour, “Finding Neverland,” “Waitress” and “Kinky Boots,” to name a few.She had a steady string of gigs until her late 20s, when the parts began to dry up. She worked as a caterer and kept going to auditions. She was one of the first people to read for the part of Diana in the workshop; she was hired virtually on the spot.De Waal was one of the first people to read for the part of Diana, and she was hired virtually on the spot.Josefina Santos for The New York Times“Jeanna has been an extraordinary partner in the process,” Ashley said. “She’s really used these couple of years to deepen her feelings about Diana, to make individual moments more and more specific in terms of the emotion of the scene. Even how she holds herself and her mannerisms have gotten more layered.”Back in New York, mid-pandemic, the long, strange delay gave the production the incidental gift of time.“New musicals can make use of the wealth of response you get from that preview period,” Ashley said. “How are the audiences responding? Where do they get quiet? Where do they get restless?” Two new songs were added; changes were made to dozens of pages of the script and lyrics.The story also shifted. Originally it focused on Diana’s disillusionment at the shattering of her happily-ever-after childhood dream. Now it is a sharper, spicier tale about a love triangle that sabotages a marriage. As Diana once said, referring to Camilla: “There were three of us in this marriage, so it was a bit crowded.”“What we have now is a much more juicy and titillating story of what this marriage was, with Charles and Camilla orchestrating the whole thing and continuing to see each other,” de Waal said. “It’s also the story of a woman’s revenge.”De Waal was just a child when her father came into her room one morning in late August 1997 and told her that Diana had been in a serious (and ultimately fatal) car accident. But in studying her for the part, de Waal has come to love and admire the princess — the way she tried to make something of her life, the way she made a difference.“Every single aspect of this show has come from a place of wanting to celebrate this person,” de Waal said. “She did a hell of a lot more than most people. Who knows where her life would have gone?” More