The Mackenzie Poltergeist at the Black Mausoleum, Greyfriars Kirkyard

Greyfriars Kirkyard sits in Edinburgh's Old Town. In 1679, after the Battle of Bothwell Bridge, about 1,200 prisoners were held south of the kirkyard, around 400 of them in the enclosure now called the Covenanters' Prison. Nearby stands the domed mausoleum of Sir George Mackenzie of Rosehaugh, the Lord Advocate known as "Bluidy Mackenzie". Architect James Smith based it on Bramante's Tempietto.

1998. The story begins with a homeless man in need of shelter who broke the lock, entered the mausoleum and opened a coffin. The floor gave way, and he fell into the pit beneath, "which contained the bodies of plague victims," before fleeing in panic. He has never been named, and no police record of the break-in has been found. Some say it was not a man at all, but children avoiding punishment.

Within a week, a woman was "blown back from the mausoleum by an icy blast of air". One account says a local resident was found unconscious outside the mausoleum gates in January 1999, with unexplained bruising on the neck. Bruises like finger-marks.

Then the reports multiplied. Visitors said they were pushed, scratched, kicked and bitten. They reported hair being pulled and limbs grabbed. Some were "hit by a cold force and strangled". Others described burns, nausea, splitting headaches, hot and cold spots, strange smells, banging noises and knocking from underground.

A few saw white figures. Cameras and watches failed. Dead animals were found near the tomb. Jan-Andrew Henderson's 2001 book, The Ghost That Haunted Itself, counted 24 people knocked unconscious over two years. Later tallies climbed into the hundreds, then the thousands.

The City of Edinburgh Council locked the Covenanters' Prison not long after the first sightings. Since then, visitors have entered only on guided tours, so that no one can be left alone to explore. City of the Dead Tours, founded by Henderson, describes itself as having sole access. Henderson says he gathered hundreds of eyewitness accounts and photographs, and is said to have been a victim himself.

Colin Grant, a spiritualist medium, came with local press watching. A candle. A cross. A Bible in his right hand. He said he had cast out the spirits.

Another account says he felt "the presence of hundreds of souls in torment and a presence of overwhelming evil" and fled the kirkyard. Several weeks later he died of a heart attack. A photograph by Susan Burrell of the Edinburgh Evening News was said to show a dark shape gliding across a window of a church that was locked, with no one inside.

Sceptics note that nearly all the documentation comes from ghost tour companies, and that Henderson owns one. On MonsterTalk, Blake Smith pointed to Richard Wiseman's research on how expectation shapes experience at supposedly haunted sites. Wiseman's 2001 study of the South Bridge Vaults found that reports clustered where people had been told a place was haunted, and where there was cold air flow, magnetic variance or particular lighting. City of the Dead guide Fred Fogarty added a twist. The Black Mausoleum, he said, is the Dundas family tomb inside the Covenanters' Prison, not Mackenzie's own. No formal hoax finding has ever been made.

On 30 June 2003, two teenagers forced their way into the Mackenzie mausoleum and cut the head off a corpse. It was a separate crime, often confused with the first break-in. The poltergeist went on to television in Extreme Ghost Stories. Henderson's title says the rest. A ghost that haunted itself.