Liz Garbus was skeptical.The documentarian behind films like “Becoming Cousteau” and “What Happened, Miss Simone?” was not an avid royal watcher. She knew the broad strokes of the decision by Prince Harry and his wife, Meghan, the Duchess of Sussex, to leave the British royal family. She had seen their interview with Oprah Winfrey. But she assumed that the stiff upper lip emblematic of elite British society would not make for a compelling documentary — too guarded, too interested in hagiography, too much of an all-around royal pain.Then she saw the footage.Encouraged by friends to document their dramatic decision to “step back” as senior members of the British royal family and assert their financial independence, Harry and Meghan shot more than 15 hours of personal video in the early months of 2020 as they finalized their plans to exit Buckingham Palace for good. Then they shared it all with Ms. Garbus and her husband, the producer Dan Cogan.Suddenly Ms. Garbus found herself watching Harry in the Windsor Suite at Heathrow Airport, addressing the camera directly. The video is dated March 11, and Harry has just finished his final two weeks of royal engagements and is headed to Vancouver to meet Meghan.“You’re right there with Harry in the Windsor Suite processing the fact that he’s leaving the royal family for the first time in his life,” Ms. Garbus said. “Then there was another clip with Meghan at …
