The main first unit filming was shot entirely on location in just 8 days.
During filming, actor Jason York (Marcus) discovered his bottle of drinking water had been mysteriously shot-through with a pellet gun on set at the asylum location, with the bullet still inside the bottle. Nobody on set had a gun, as weapons were expressly forbidden from the set.
The dead badger was a real dead badger that the filmmakers found on their way to the filming location on the first day, and decided to use it in place of other dead animals used in the scene (rats). They named it Helga, and once they were finished filming with it they buried it in the grounds of the asylum location.
Actor Richard Goss previously worked with the filmmakers on Taking Care of Business (2016) in which he played the lead character of 'Toby'. In this film he has a cameo appearance as the gas station cashier, who's name badge reads the name 'Toby'.
Featured heavily in the E4 television series Stage School, which featured director Gene Fallaize and producer Tony Cook casting roles for the film.