Just answered a knock at the door to find a young lad aged about 12 standing there. We'd left the front door ajar on a security chain to allow some fresh air into the house and he and his 2 chums had seen it and thought they ought to warn us our front door was open just in case any dodgy people were about. I thanked them all for their concern and was left thinking how nice it was that they took the time to tell us. I'm hoping they weren't casing the joint...