This same quote struck me as odd, but for a different reason, especially as there is an aerial view of the house and river in today’s papers. I assumed the river was behind the house- but it’s actually over some common land in front of the house- so he left by the back door and then went presumably around the side of the house and through the front garden- why would a five year old have that logic- surely if they were off to play in the garden they would still be in said garden, if leaving to the river the obvious route is through the front door. That’s based on it being accidental and he left the house to go explore outside, rather than any suspicious circumstances.