Investigators set up camp in a bid to probe the mystery of a ghost said to haunt a historic Newcastle building.

The team was headed by Tony Liddell, from Leadgate in County Durham, who last year wrote a book on paranormal vigils in the North-East.

His most recent all-night assignment was the Assembly Rooms. The building, opened in 1776, was the alleged scene of a tragedy when a lady threw herself off a balcony. Stories of a so-called Grey Lady walking through the building have been reported over the years.

Antony Michaelides, owner of the venue, said: "We have never found documentary proof of exactly who the lady was or when this happened - it's just one of those stories that becomes accepted over the years - but there have certainly been some unexplained events, such as sounds, air movements and even sightings of apparitions which my staff have experienced at various times, so we welcomed Tony's offer to investigate these happenings in a scientific manner."

Tony and his team of six investigators set up their equipment of 35mm and digital cameras, night vision camcorders with infra-red boosters, ultrasound recorders, electromagnetic field meters, ambient and laser temperature recorders, and digital dictaphones.

Tony said: "The Grey Lady story has always interested us and we recorded a variety of paranormal activity. This included a 10 degree instant drop in temperature in one room coinciding with a light anomaly - a bright light that moved out of the room and down a corridor.

"There were also 11 separate instances of repeated requested noises. By this we mean if an unexplained noise is heard, the investigator asks if it can be repeated, which it was, a few times and then asks the same question after a long gap, and again the noise was repeated.

"We also had two camcorders physically switched off for no explainable reason and we have a photograph of another light ball above a table, the appearance of which coincided with a loud crash. There have only been three times over the last two years or so since we began researching the paranormal where I have really been shaken, but there is certainly some activity in the Assembly Rooms, although I should add that nothing we saw would suggest that it poses any danger to guests.

"There is obviously a certain amount of scepticism about the work we do, and we actually like nothing better than being able to prove unexplained occurrences have a perfectly natural reason, as happens occasionally, but we do use highly scientific methodology and modern equipment in our investigations. Whether people believe the results or not is up to them."

Tony is working on a second North-East book due to be published next year.

Mr Michaelides said: "I've never seen the Grey Lady, but I do believe the accounts that I've heard from staff working late at night. I think it all adds a bit to the romance of this fantastic old building and we wouldn't try to get rid of her even if we could."