When a clock fell off the wall in Hoyland Town Hall in South Yorkshire, few gave it a second thought - until the caretaker discovered a miniature spy camera hidden behind it. So why was it there? Was it a case of foul play in a council argument? Or something more high-level? Steve Punt turns detective to tackle the Hoyland mystery. He tests out a range of theories - including the idea that it was placed there by the security services during the miners' strike. Producer Laurence Grissell