Factual error: Although set in 1860, virtually all the costumes/clothing in the film are far more typical of the later Victorian period. For example, the police are wearing cork helmets, tunics, and Duty Armlets with upright stripes. These items were not introduced into the Metropolitan Police until 1863, 1864, and 1886 respectively (and this would have been delayed further in a small backwater Cornish town). In 1860, they would be wearing top hats, swallow-tail coats, and Duty Armlets with horizontal stripes.
Other mistake: When Sir James examines a book on witchcraft in the Vicar's library, it is a photographic reprint (more contemporary to 1966) of a much older, original book.
Sir James Forbes: High-ate-ee is how he pronounces Haiti.