Eileen Dietz who played the Demon in the Exorcist had all her scenes cut in the final film but she can still be seen at the end of the teaser trailer.
Craig Rees's Mother passed away from Leukemia whilst the film was in production. The film is dedicated to her.
Lead Actor and Director Craig Rees was convicted and sentenced to seven years in prison, April 8 2024, in what the BBC calls a 'film tax fraud' operation. 'Whispers' (2015) was one of the films discussed in court and according to the court part of their fraud, alongside two others - 'The Eight', and 'Violence'. Rees was trialed at Birmingham Crown Court, however he fled the country during proceedings, likely fleeing to Ukraine.
Actor Rupert Evans was almost cast as Simon but backed out due to other filming commitments.