Goofs

(at around 11 mins) As Mary and Angus walk home through the grove after the party, Lady Sylvia's Jaguar passes them. Startled, Mary comments on the car and mentions its headlights being off, though they were clearly on in every shot of the car.

Mary later states that the headlights were "hooded". Hoods were used in Britain during the Blitz.

When Lady Sylvia is attempting to sacrifice Eve, her head gear disappears and reappears randomly.

(at around 1h 20 mins) When Eve is tied up and waiting to be sacrificed, Lady Sylvia places the Dionin skull next to her and walks away. Several seconds later the skull disappears while Eve is struggling to get away, but it reappears when Sylvia returns.

(at around 1h 19 mins) When Angus has a mongoose thrown at his face, he clearly loses his glasses before falling down. In the next shot, Angus on the floor, his glasses are on his face, perfectly well positioned.

(at around 1h 16 mins) When Angus runs out of breath, the pipes shouldn't have stopped because the bag could hold air long enough for him to catch his breath again.

(at around 1h 19 mins) When Lady Marsh takes the earplugs out of her ears, the skin in the inner ear is not made up and is clearly pink, while the rest of her is painted blue.

(at around 1h 19 mins) When Lady Sylvia Marsh attacks Angus Flint, you can see Sylvia has one evil eye on the right, but on the left, eye is normal.

(at around 1h 3 mins) Lord James searches through a collection of ancient 78-rpm shellac discs. Although he plays one of the discs on a modern-day turntable that is capable of playing them, the music heard is electronic-based and has excellent fidelity. However, shellac records had notoriously low sound quality and were discontinued decades before synthesizers were used regularly in music production.

(at around 1h 16 mins) Angus's fingers are not moving on the chanter of the bagpipes while he is luring P.C. Erny around the sundial.

Around 52 minutes in Equipment visible in Lady Marsh's glasses when she is in the tree.

The snakes used in the film are not native to the United Kingdom nor are they venomous.

(at around 4 mins) After excavating the skull Angus says that the ancient Romans missed the dinosaurs by 25 million years, while it's in fact 66 million years.

(at around 40 mins) Dissociative identity disorder is erroneously referred to as schizophrenia.