Sally Hawkins and Timothy Spall join Princess Diana biopic Spencer

Sally Hawkins and Timothy Spall have signed up to star in the upcoming Princess Diana biopic Spencer.

Kristen Stewart is playing the beloved figure in the flick, helmed by director Pablo Larrain, and now British acting royalty has boarded the highly-anticipated drama, according to Deadline.

Spall and Hawkins, along with Mission: Impossible – Fallout star Sean Harris, will be playing fictional characters, not members of the Royal Family, editors at Screen Daily report.

The film, penned by Peaky Blinders creator Steven Knight, focuses on a weekend at the Royal Family's Sandringham Estate during Christmas 1991 when Diana decided to end her marriage to Prince Charles, the father of her two children, Princes William and Harry.

Stewart said the biopic was an "emotional imagining" of the turmoil Diana was in during a pivotal point in her life, as she decided to embark on a path away from royalty.

"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," she said in a statement.

Charles and Diana separated in 1992, and were divorced in 1996.

The international icon was tragically killed at the age of 36 in a collision in the Pont de l'Alma tunnel in Paris on 31 August 1997, while fleeing the paparazzi with her partner, billionaire businessman Dodi Fayed, and their driver, Henri Paul.

The first picture of Stewart as Diana was released on Wednesday, and filming is underway in Germany, with production due to relocate to the U.K.

Spencer will be released in autumn 2021.