Continuity mistake: When Rosemary visits Hamilton Teed, he shows her a picture of Martin and Jim, aged 10, then puts the photo down on the desk, but a second later, the photo is gone.
Continuity mistake: When the girls are just finishing their look of the walled garden, Laura's scarf that has been visible on both sides up until now vanishes on the left side, then it comes and goes repeatedly.
Continuity mistake: When Laura finds the hammer with blood and hair on it, Rosemary finds the constable and tells him where the hammer is. When we first see the constable's car, it's in a ditch. But when he gets into it and drives away, it's no longer in the ditch, but beside the road.
Continuity mistake: About halfway through, when the girls are sitting at the dining-room table and Martin walks in with a decanter of red wine, he proceeds to fill the girl's glasses, but not his own, and yet, in the next shot, his glass is filled.
Continuity mistake: In the beginning, the Land Rover has something on the roof, like a ladder, but not long afterwards there's nothing on the roof.
Answer: Regents park.