Tony Robinson was investigating the paranormal on TV last week. At one point a professional sceptic offered to show how spiritualist seances were worked. A bunch of stooges sat round a table in total darkness, the "medium" called for a spirit to manifest itself and the "medium"'s assistant came in- soundlessly- and moved some objects around. This was supposed to prove that the famous, physical medium, Helen Duncan- who sat in semi darkness and produced ectoplasmic manifestations of actual, dead people- was a fake. When Robinson pointed out there was a certain disparity between knocking things over in the dark and producing walking, talking spooks, he was told that Duncan's sitters were obviously imagining things. Ah, but of course.