The old man told the story of when he was foreman at Croziers in ChCh prewar - the Austin agents. Austin 10 with a rattle no-one could find. He pulled out all the seats except the drivers and got an apprentice to drive him round town while he crawled around the interior. Tracked it to a B pillar. Cut it open and there was a 5/16 whit bolt sitting in there. Someone on the assembly line playing silly buggers.