Monument MPM1917 - Sea Line Wall, Gunwharf

A section of the 17th century Sea Line Wall was revealed during an archaeological watching brief at Gunwharf Quays in 2002. The wall had been situated on the west side of the remodelled Portsmouth town defences designed by Sir Bernard De Gomme and constructed between 1668 and 1685. It incorporated three bastions with gun emplacements (a triangular bastion in the centre and angled bastions at either end), and was designed to protect both the inner defences from vessels trying to land on the seaward side, and the road which ran from the town to the dockyard. It replaced a series of earlier walls that had stood on the site since the early-16th century.

Large sections of the wall were demolished/buried when New Gunwharf was built between 1797 and 1810. The new quay wall was bonded into the face of the Sea Line Wall and its northern end formed part of the Basin between the Old and New Gunwharfs. 20th century services further damaged the wall, truncating it in places.

Approximately 40m of the wall was observed during the watching brief. The central section had survived in a good state of preservation to 2.26m O.D. The northern end had been heavily truncated by 20th century service trenches and survived only as a line of degraded rubble core. The southern section had also been truncated but was preserved to approximately 1m O.D.

The wall had been constructed using rectangular limestone blocks, the faces of which were dressed and the backs roughly shaped. It had a limestone rubble core. The upper level of the wall was approximately 1.8m wide. The full depth of the wall was not observed.

Barge, Melanie, 2002, Canalside Blocks Gunwharf Portsmouth: Report on the Archaeological Watching Brief (Unpublished document). SPM519.