Factual error: A few days prior to Warrens' visit to the Hodgson's family, Janet watches the British comedy TV series "The Goodies" on TV. The episode that she was watching actually aired on December 22 of the year in the UK. Later, when Ed records the interview with Janet, it turns out that it's December the 21st. (00:28:20 - 00:31:25)
Factual error: No council house in Enfield has a cellar like that.
Factual error: Fireplaces in the house are not those of a 1930's British house, they are the wrong size (more USA dimensions). You'll never see a British tiled fireplace quite like that.
Factual error: The school sign, supposedly in the 70s, is showing an 11 digit telephone number. The number should only have nine digits in the 1970s.
Factual error: All four Hodgson children go to Enfield Grammar School. Enfield Grammar School is a single sex boys' school, so the two girls could not go there. In addition, grammar schools in England are secondary schools. While the two girls (aged 11 and 14) are of secondary school age, their younger brothers are of primary school age.
Answer: Valak was portrayed as a particularly powerful demon. In horror films demons are often portrayed as overconfident, and in this case it was thinking that Lorraine Warren would not be powerful enough to be able to defeat it. In addition, Valak revealed their name while Lorraine was in a dreamlike trance state, so it may have believed that she might not remember or make the connection at any point and be able to use it to her advantage.
dewinela