From riderless horses disappearing through castle walls mischievous spirits apparently barging into visitors, English Heritage has compiled a new survey of "hauntings" and unexplained events recorded at its sites.

Whilst popular ghost stories have previously been associated with some of the sites, this stocktake is thought to be the first time that staff at English Heritage, the government body charged with managing historic buildings, have been asked to log specific incidents reported by workers and visitors.

There have been so many sightings of mysterious figures in the labyrinth of tunnels below Dover Castle, in Kent, there staff there have created an established procedure for dealing with them.

On one occasion, a school group which had just been round told me about an historical re-enactor they had seen, dressed in monks’ robes.

"But there was no such re-enactor on site. It couldn’t have been another visitor. I can’t really explain it.