Monument MPM37 - Spur Redoubt

Spur Redoubt was built in the 1680s to strengthen the seaward line of defences. The redoubt was modified 1730-1750 and the ground plan was changed from equilateral to triangular. In 1865 the redoubt was equipped with 5 guns covering the harbour approach, plus three smaller gun emplacements on the western side to cover the harbour itself. It was demolished in 1930 when the seafront promenade was extended across the area, but the remaining masonry was exposed and restored in 1988.

Part of the remodelled fortifications designed by Sir Bernard de Gomme, Spur Redoubt was built in the 1680s in order to strengthen the seaward line of defences. The ground plan of the redoubt was originally equilateral. This was changed to a triangular plan when the seaward side was extended when the redoubt was remodelled to the designs of John Peter Desmaretz between 1730 and 1750. [1]

A communication tunnel which connected the redoubt with the Square Tower, via Ten-gun battery, has been said to still exist beneath the promenade [1]. A linking wall (MPM2142) between the Saluting Platform and the Long Curtain seaward wall (see record for Long Curtain MPM1757) has been described as a caponier that formed part of this passageway. However, no such tunnel was noted during an investigation at the Saluting Platform and no evidence was apparent when a section of the Long Curtain seaward wall was breached in 2014. [2]

According to a plan dated c1865 the structure could accommodate five guns to cover the navigational channel, plus three smaller gun emplacements on the western side to cover the harbour. The redoubt remained operational until the 20th century, and was demolished in 1930. The lower courses of the structure were exposed and restored during urban regeneration work in 1988. [3]

Most of the upper structure of the redoubt was removed when a public promenade was construced in 1934 and the surviving lower section was hidden beneath a car park until restoration work was undertaken in 1988. The redoubt measures 46.40m along its west facing elevation and 49.15m along the south facing elevation. The surviving walls are an average of 2m high. It is thought a further 2m of the upper structure was lost when the promenade was built. [2]

--------------------------------------------------------------------------------------------------------------------------------------------------------------

Restoration work in 1988 revealed the redoubt had been built on a man-made shingle bank, with roughly dressed Portland/Purbeck limestone walls. A flight of steps, also constructed from limestone, had been used to access the upper gun platform from a covered area at the rear.

A magazine constructed from red brick walls with a barrel-vaulted roof six bricks thick, was thought to be part of the original 17th century structure. This had been extended in the mid-18th and mid-19th centuries.

A wall dating to the 18th century modifications was exposed. This had also been constructed from Purbeck limestone, but used a heavier squared-ashlar technique. This added 5m to the thickness of the seaward wall. A sally port giving access to the beach on the south side had been incorporated in to the south-east corner of the Spur when it was rebuilt between 1730 and 1750.

Another feature which might have dated to the 1750s was a guardroom constructed from red brick. A brick-built open fire in the south-west corner of the room had been modified during the mid-19th century when a small cast-iron range had been added.

[3, 4, 5]

--------------------------------------------------------------------------------------------------------------------------------------------------------------


A watching brief was undertaken at Spur Redoubt during work for the Southsea Coastal Defence Scheme between 2021 and 2023 when more of the walls were temporarily exposed [2, 5]. Only a basic recording was carried out during the works as a more extensive recording had been undertaken during the partial excavation and renovation of the redoubt in 1988. This recorded that the wall of the redoubt had been constructed of ashlar limestone blocks laid in regular courses which had been frequently repaired and reconstructed, including during the course of the coastal defence works.

Evidence of 19th century renovation work was recorded in a trial hole excavated adjacent to the redoubt. This revealed the section of wall at this location had been underpinned with bricks.

Four small sections of wall were interpreted as belonging to 19th century garden accommodation within the redoubt. A mixture of building materials had been used to construct the foundations which suggested the walls had been built at slightly different times using whatever material was available.

[6]

<1> Patterson, B.H., 1987, A Military Heritage A History of Portsmouth & Portsea Town Fortifications (Bibliographic reference). SPM43.

<2> Flood, Grace, 2024, Southsea Coastal Defence Scheme Sub Frontage 1, Southsea, Hampshire: Historic Building Record (Unpublished document). SPM662.

<3> Fox, R, 1991, Portsmouth's Ramparts Revisited (Bibliographic reference). SPM351.

<4> Portsmouth City Council, n/a, Portsmouth City SMR Cards, SZ69NW36 (Index). SPM1.

<5> Portsmouth Museum Service, 1988, Spur Redoubt (Excavation archive). SPM21.

<6> Williams, Rachel & Tuck, Ashley, 2023, Southsea Coastal Defence Scheme Sub Frontage 1, Southsea, Hampshire: Archaeological Watching Brief (Unpublished document). SPM643.