Sandy was impressed. Her son, John, had never thrown a ball back like that before - so hard and fast that it bypassed her completely and flew over the wall at the bottom of the small garden they shared. "Nice one, Johnny!" she yelled. "Let me go and get it, I'll be right back!"
She yanked open the wooden gate recessed into the red brick wall and entered the narrow alleyway at the back of her house - and all the other houses like it. She looked left and right and spotted the ball rolling away from her, towards the...