The spookiest for the company’s 1,800 staff was Bolsover Castle in central England, which is built on top of an ancient burial ground.
One staff member said she heard a scream which became louder as she walked away from the castle but when she rushed back she found no one there.
Security guards also said they were alarmed by unexplained lights and some staff said they saw the ghost of a little boy holding the hands of unknowing visitors.
The ghosts of a young boy and a woman have been seen in the ruins of Kenilworth Castle. Some employees said they also saw an antique cot rocking itself.
In Carisbrooke Castle on the Isle of Wight in southern England, ghostly apparitions are common.
The pale disembodied face of Elizabeth Ruffin, a young girl who drowned in a well on the site, has been spotted, as well as the “Grey Lady”, a phantom wearing a long cloak accompanied by four dogs.
In Pendennis Castle in Cornwall in southwest England, visitors reported hearing the piercing cries of a kitchen maid who fell to her death when the castle was under siege for six months in the 17th century.
Whitby Abbey in northern England, whose Gothic ruins inspired Bram Stoker, author of “Dracula”, has unexplained cold draughts, stock flying off the shelves and strange taps on the shoulder seemingly from no one.
At the home of Charles Darwin, the British 19th century naturalist, a staff member reported that a quill that lay on the desk suddenly started spinning and would not stop until she left the room.