Eerie black shapes seen in the Keep

I was talking to one of the conservators at Penrhyn Castle a few days ago and I asked whether anyone had seen anything ghostly since I was last there. He said that he often sees things out of the corner of his eye, which he says are dark shapes moving just to the side of him, as though he is being followed around as he does his work. I asked where he sees these shapes and he said that it is mostly in the Keep, which is an area of considerable ghostly activity, where lots of staff and visitors have seen things. He has not been able to identify anything specific but he often has an uneasy feeling as though he is not alone and is being watched. He told me that he wonders whether he imagines the shapes but they appear when he is not thinking about anything to do with ghosts and it happens quite regularly. Very creepy! I wouldn't want to be up in the Keep on my own after all the things people have experienced in there! I will ask him more about it when I am next at the castle.