The ghost sequence was not achieved using digital or optical effects. It was captured 'in camera', using a Victorian stage technique called 'Pepper's Ghost': Jim Howick's performance was reflected onto a sheet of angled glass, positioned in front of the camera, while Mat Baynton performed behind the glass.
Mathew Baynton, Simon Farnaby, Martha Howe-Douglas, Jim Howick, Laurence Rickard, and Ben Willbond are a writing and acting team that also worked on Horrible Histories (2009), Yonderland (2013), and Ghosts (2019).
Monty Python e il Sacro Graal (1975) was a huge influence on the filmmakers, if only as an example of how to make a historical film on a tiny budget.
The Earl Of Croydon quotes Obi Wan Kenobi when he rescues Anne from the muggers: "Poor people are easily startled but they will return and in greater numbers".
One of the writers, Laurence Rickard, is a huge fan of Star Wars, hence the various references within the movie to the franchise.