When I visited George Barnsley & Sons Cornish Works in Sheffield over 2 years ago it ranked as one of the most time warped explores I had ever encountered. In places the building retained Victorian features such as gas lights and other wonderful features. The building amazingly ceased to be used in 2004 and only because the current owners could not maintain the upkeep of the buildings. Sadly in the years that have past since that first visit the place has suffered from vandalism, theft and generally is in much poorer state than it once was.
