The accident happened at around 8am yesterday (25 January). He was taken to hospital but died later from his injuries.
Police and the Health & Safety Executive’s Mines Inspectorate are investigating.
Local press reports say that the 58-year-old man was doing contract work at the museum, where an underground roadway for visitors is being extended in a £2.7m lottery funded project.
The work was due to be completed in the next couple of weeks.
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