Mary Shelley (2017)

Factual error: Allegra was said at the end of the film to have died aged 10. She was actually 5 years old when she died.

Factual error: At the end, it is stated that Mary was buried with her parents. Mary was not buried with her mother and father upon her death despite wanting that for herself. She was instead buried at St Peter's church in Bournemouth. Her coffin was later exhumed and relocated to meet her final wishes.

Factual error: At the end, it is said that John William Polidori committed suicide due to not receiving credit for The Vampyre. This is not confirmed as the coronary report concluded the death to be natural despite evidence to the contrary. He was also plagued by gambling debts which caused him depression which may be a more (or equally) plausible reason for his alleged suicide.