At the locked gate, Mrs McCarthy suggests Bunty to pick the lock, but she refuses, even though she has the know how. A bit later, when they are in front of another locked door, Father Brown and Inspector Mallory dying behind it, neither of them even thinks about the lock-picking and they end up blowing up the door.
When Sergeant Goodfellow is reviewing the Haggard file on Inspector Mallory's desk, he reads a newspaper clipping about the murder. Mr Haggard's age at the time of his death is given as 58 years. Later, Mr Haggard's gravestone in the churchyard shows his birth year as 1901 and death year as 1951, making him only 50 years old.
Despite Spencer Hall having lain empty for around two years, the gardens, and the lawns in particular, have obviously been tended. Inside the house there seems to be no dust, noticeably on the black Bakelite telephone.