David Seidler, who drew on his boyhood struggle overcoming a stutter to write the Oscar-winning screenplay for “The King’s Speech,” the hit 2010 drama about King George VI’s effort to subdue a stammer while rallying the British people against Hitler, died March 16 during a fishing trip in New Zealand. He was 86.

His death was announced in a statement by his manager, Jeff Aghassi, who did not give a cause. Seidler, who lived in Santa Fe, N.M., had been diagnosed with bladder cancer in the mid-2000s. “David was in the place he loved most in the world – New Zealand – doing what gave him the greatest peace, which was fly-fishing,” Aghassi said. “If given the chance, it is exactly as he would have scripted it.”

With “The King’s Speech,” Seidler dramatized the relationship between the emotionally vulnerable king-to-be, Prince Albert (Colin Firth), and his imperturbable speech therapist, Lionel Logue (Geoffrey Rush), who helps the future George VI learn to manage his stutter. The film culminates with a wartime radio address in which the new king reassures the nation at the outset of World War II, speaking fluidly – with guidance from Logue – while stammering slightly on Ws.

“Had to throw in a few,” the king explains, “so they knew it was me.”

Directed by Tom Hooper, the film grossed more than $420 million worldwide and became the first hit movie penned by Seidler, a British-born writer who grew up on Long Island, tamed his stutter at 16 and took a circuitous journey to Hollywood, with stints as a political adviser for the prime minister of Fiji and creative director for a New Zealand advertising office. The movie received 12 Oscar nominations and won four, including best picture and best original screenplay for Seidler, who at age 73 was one of the prize’s oldest recipients.

“My father always said to me I would be a late bloomer,” he joked in his speech, before accepting the Academy Award “on behalf of all the stutterers throughout the world.”

“We have a voice,” he continued, speaking in a mellifluous baritone that seemed to belong to an actor, not a writer. “We have been heard.”

The film was credited with shifting public perceptions around stuttering, which had been depicted on-screen for comic effect through characters like Porky Pig, and had also been used to suggest that a character was somehow cowardly or inadequate.

Seidler knew otherwise, having dealt with the speech condition ever since he was a toddler. The summer he turned 3, in 1940, he and his parents left Britain for the United States, fleeing what they feared was an imminent German invasion. They sailed aboard a three-boat convoy, and one of the ships was sunk by a German U-boat, according to Seidler, who developed a stutter around the time they arrived in New York.

Working with a speech therapist, he tried to treat the condition using some of the techniques he later incorporated in “The King’s Speech,” like speaking with a mouthful of marbles or smoking cigarettes. (He picked up the habit at age 12 and stopped when he was 40.) His breakthrough, which he also used for the screenplay, came when he discovered cursing as a means of catharsis.

“I resolved that if I was going to stutter for the rest of my life, people were going to be stuck listening to me,” he told the Jewish Journal in 2010. “I had been depressed, but now I was angry – I decided I deserved to be heard. I learned some expletives, and I’d just leap around my bedroom like Tom Cruise in ‘Risky Business,’ shouting the f-word. And when I did, I didn’t stutter.”

Ever since he was a boy, Seidler considered George VI a hero, reading about the king and listening to his speeches with encouragement from his parents. He began thinking about a script while in college and was writing it in earnest by the early 1980s, when he tracked down Logue’s surviving son, Valentine, who offered to give him the speech therapist’s notebooks for his research.

Valentine had one request: that Seidler obtain approval from the king’s widow, Queen Elizabeth the queen mother. Replying in a letter, she asked him not to pursue the project during her lifetime, saying that the memory of those years was “too painful.”

“This is where the Brit side of me comes in,” Seidler recalled in an interview with Script magazine. “If the Queen Mum says wait, you wait. And besides, I didn’t think I had to wait that long.” He waited about two decades before her death in 2002, at age 101.

Seidler soon returned to the project, making headway after Jacqueline Feather, his longtime writing partner and then-wife, suggested he turn his draft into a stage play, focusing on the central relationships. That led him to pursue parallel versions of “The King’s Speech,” which premiered onstage in 2012, briefly running on London’s West End, after the film version was further refined with help from Hooper, who worked with Seidler on some 30 different drafts.

According to Seidler, the decades-long process of conceiving and writing the screenplay was worth it for a story that needed “a more mature writer” than the one he was when he started.

“This required going back into the pain and the loneliness and the isolation and frustration of being a stutterer,” he told CNN. “And being a stutterer is rather like having a very bad toothache. When you’ve got the toothache, all you’re thinking about is ‘Wow, my tooth really hurts.’ All I can think about is that pain. As soon as you get to the dentist and the dentist fixes it, the last thing you want to remember is how that tooth ached. You just blank it out, the mind forgets it.”

David William Seidler was born in London on July 13, 1937, according to his manager, although other sources give his birth date as Aug. 4. His mother, the former Doris Falkoff, was a graphic artist whose work was acquired by museums including the National Gallery of Art. His father, Bernard, was a fur broker whose Jewish parents were killed in Nazi concentration camps.

After the war, the family settled in Great Neck, N.Y., where Seidler shed his stutter while in high school, successfully auditioning for a school play the next week. He studied English at Cornell University, received a bachelor’s degree in 1959 and earned a master’s degree at the University of Washington the next year.

His marriages to Mary Ann Tharaldsen, Huia Newton and Feather, his collaborator, ended in divorce. Survivors include a son from his second marriage, Marc; and a daughter from his third, Maya.

Seidler wrote dubbed dialogue for the American release of Godzilla films and got his first screenwriting credit in 1966, working on a seafaring Australian series called “Adventures of the Seaspray.”

By his own acknowledgment, he made some “not brilliant career choices,” often taking paycheck jobs while trying to support his family. He had credits on nearly a dozen TV movies, including “Onassis: The Richest Man in the World” (1988) and “Come On, Get Happy: The Partridge Family Story” (1999), as well as a handful of features, including the animated movies “Quest for Camelot” (1998) and “The King and I” (1999).

His first feature, “Tucker: The Man and His Dream” (1988), ended in personal and professional disappointment. Directed by his high school friend Francis Ford Coppola, the movie told the story of automobile entrepreneur Preston Tucker and took years to get off the ground. Seidler had what he called “a terrible falling out” with Coppola and sparred with co-writer Arnold Schulman over credit on the picture, which received positive reviews but flopped at the box office.

Seidler was still working in recent years, with uncompleted projects that included a Miles Davis film and a script about Lady Hester Stanhope, an aristocratic British adventurer. Another project brought him back to themes of “The King’s Speech,” examining the relationship between a political leader and a commoner, albeit in very different circumstances. The script was based on a 2023 documentary, “Hiding Saddam Hussein,” about the former Iraqi dictator and the farmer who helped him evade capture for eight months.