The film, which is eyeing a fall 2021 release, is set over the course of a weekend in December 1991, when Princess Diana joined the royal family for Christmas as the Sandringham Estate -- and decided to leave her fractured marriage to Prince Charles. Speaking about the film, Stewart had said, "Spencer is a dive inside an emotional imagining of who Diana was at a pivotal turning point in her life. It is a physical assertion of the sum of her parts, which starts with her given name; Spencer. It is a harrowing effort for her to return to herself, as Diana strives to hold onto what the name Spencer means to her."