Final performance of Diana Rigg, who passed away on September 10, 2020. The film is dedicated to her memory. Her only child, actress Rachael Stirling, receives a "Special Thanks" in the end credits.
The scene where Eloise first sees Sandie through the mirror is done practically. To achieve the mirror effect, the cloakroom attendant is played by twins James Phelps and Oliver Phelps.
During the end credits shots of a deserted, empty, central London flash on screen. All of these shots were completed during the COVID-19 global pandemic. The empty streets are as they were, as England at the time was in a national lockdown.
Anya Taylor-Joy does her own singing when Sandie performs in the film.
To achieve the shots of the students walking down the nighttime Soho streets, the crew hid a Steadicam within a bicycle rickshaw taxi (these are common around the Soho area). The road was not closed off and the 'extras' in the shot were unaware they were in a movie.