Six went in...only one came out.The Standedge Tunnel, the longest canal tunnel in England, has become one of the rural village of Marsden's main tourist attractions. Now it's also a crime scene.Six students went into the tunnel on a private boat. Two and a half hours later, the boat reappeared at the other end of the tunnel carrying only one of the students, Matthew. He had been knocked unconscious and has no memory of what took place...