Police are appealing for information after a sheet of waxed tarpaulin was stolen from the grounds of Carew Castle.
The tarpaulin, which is green in colour, measures 24 feet by 16 feet, and was taken sometime between 6 pm on January 26 and 6 pm the following evening.
It was being used to protect a newly-built stone wall and was secured with ropes to a metal structure, which belongs to the Pembrokeshire Coast National Park Authority.
Anyone with any information is asked to contact WPC Sweeney at Tenby police station on 842303.