Princess Diana's former bodyguard Ken Wharfe on Stewart's performance: "Out of all the people who have played Diana over the past 10 years, she's the closest to her. She managed to perfect her mannerisms."
The candlelight family game night scene between Diana and her sons William and Harry was structured but not completely scripted, so Kristen Stewart and her co-stars Jack Nielen and Freddie Spry were given the freedom to improvise, and the entire scene was ad-libbed.
According to Kristen Stewart, at the end of the first week of filming she felt that: "This is the best thing I've ever done. This is the most alive I've ever felt." (New York Times 11/6/21)
Director Pablo Larraín had Kristen Stewart watch Gena Rowlands' performance in A Woman Under the Influence (1974) to prepare for her role.