Work has begun to repair a unique, 16th century causeway in the Pembrokeshire Coast National Park.

The causeway at Carew Castle and Tidal Mill, which is a public footpath, has been closed while the essential restoration work is carried out.

The ancient structure is Grade II* listed, and is part of the only remaining Tidal Mill and Causeway in Wales, dating back to 1541.

The mill pond is subject to annual inspection under the Reservoirs Act 1975 and this year's inspection revealed emergency repairs were necessary. Voids had opened up in the causeway due to the continual scouring of the tidal waters through the structure.

The repair work involves drilling into the causeway and sluice and pressure-grouting the voids.

Carew Castle, Mill and Causeway are leased and managed by the Pembrokeshire Coast National Park Authority.

Andrew Muskett, the authority's building projects officer, said: "The causeway at Carew is unique; it's an ancient structure which needs constant care and attention. It has to endure an aggressive environment - not only is it trodden by walkers every day of the year, but it is also subject to daily wear and tear from the tidal waters of the mill pond.

"Over time that will take its toll and this year our consultant engineers, Atkins, highlighted areas of concern and a major inspection then revealed damage that was deemed to need emergency repair."

The work is expected to take five weeks and, as the causeway is part of a popular circular walking route, if work is not completed by Christmas, the causeway will be reopened temporarily and closed again for work to be completed in the New Year.

The repair work to the sluice, auxillary spillway and area next to the basement steps at the side of the mill is being carried out by Llanelli-based contractor Quantum Geotechnical. The sluice gates to the mill pond will also be removed, repaired and replaced.

For more information about the work, contact Andrew Muskett on 0845 345 7275.