Monument MPM1684 - Stone arches, King's Mill

The remains of three limestone arches belonging to the Portsmouth town defences built 1668-1685, revealed during an archaeological evaluation at the Gunwharf Quays site in 1997. The arches were constructed to accommodate sluices belonging to the King's Mill.

The remains of three stone arches were observed during an archaeological evaluation at the Gunwharf Quays site in 1997. The arches had been constructed against the west wall of the King's Mill (see MPM1013) and formed part of the Sea Line and Mill Redoubt section of the Portsmouth town defences designed by De Gomme between 1668 and 1685. They had been constructed to accommodate pre-existing sluices belonging to the mill (see MPM1685).

The remains of the arches consisted of four stone abutments built from large limestone blocks set in a lime-based mortar. Each abutment had an angled stone at the top, which would have formed a 'springing' (the point at which the arch rises) for each arch. The arched openings had been blocked with brickwork, probably after the mill was destroyed by fire in 1868, and had been partially dismantled during the late-19th/early-20th century.

The central opening of the structure measured 3.46m wide, the height to the springing c2.25m, and c3m to the top of the opening. It had a radius of 2.4m. The openings measured 1.78m wide on the north and 1.65m on the south side. The radius of each of the arches would have been c1.2m. It was not possible to excavate the bases of the abutments, but they were thought to be at least c3.76-86m deep, the same depth as the base of sluices encountered to the east of the mill (see MPM1685).

The remains of the arches and the wall which would have sat above them were present in the fill adjacent to the abutments. These comprised large blocks of worked stone, including a keystone and several large voussoirs (wedge shaped stone used in the curved part of the arch).

Accession No: 2013/112

The Conservation Practice, 1997, Gunwharf Quays, Portsmouth, An Archaeological Evaluation. Part Two: Site Investigation (Unpublished document). SPM326.