Monument MPM387 - Town Mount Bastion

The Town Mount Bastion, sometimes refered to as 'The Great Bastillion', was in existance by the Tudor period and appears on 16th century maps of Portsmouth. Originally an earthwork, it defended the Town Gate at the northern end of the High Street, which controlled access to the road to london. It had been enlarged by 1568, and is thought to have been the first example of an Orillion type bastion in England. When visiting Portsmouth in the 1560s, John Leland described the Town Gate and Mount as a timber gate and a ditched earth mound with guns defending the landward entrance to the town. During the 17th century the Mount was incorporated into the new defences designed by De Gomme in the 1660s. The defences were remodelled again by Demaretz during the mid-18th century. The town defences were demolished during the c1860s/1870s. [1] -------------------------------------------------------------------------------------------------------------------------------------------- A watching brief undertaken on the site of the former Students Union in 2004, revealed the remains of what was thought to be part of the forward facing wall of the east side of the Town Mount Bastion (located at approximately SZ63609964 and SZ63619961). Two sections of massive stone walls were uncovered in trenches (running north-south) in the western half of the site. One section of wall was 2.8m thick and bonded with lime mortar. It had been faced with limestone on its south side, and had a coarse, possibly destroyed, face on its north. The second section of wall was constructed from limestone, over 2m thick, with stone facing on its south face. It survived in three parts, possibly resulting from variable demolition. The north face had been partly destroyed, and a dump of foundation rubble was found to the north of the wall. Beyond the walls would have been a moat. The only evidence found during the work that possibly related to this feature were two gravel layers, which may have resulted from the infilling of the moat. As the backs of both of these walls (west side) retained their facing blocks, while the east sides had been destroyed, it is possible that the latter had been pulled into the moat. Accession number: 2004/962 [2] ------------------------------------------------------------------------------------------------------------------------------------------ An archaeological evaluation in Ravelin Park in 1972 revealed the remains of part of the north facing wall to Town Mount Bastion, the moat that surrounded it and part of the counterscarp wall. See MPM1878 for details. [3] --------------------------------------------------------------------------------------------------------------------------------------------- The remains of the post-medieval bastion wall and moat were recorded during archaeological investigations by AOC Archaeology in 2018-2019. Evidence of the demolition and robbing out of the walls, and infilling of the moat during the mid-19th century was also recorded. The bastion wall, which supported the inner side of the moat (scarp), had been constructed using roughly coursed limestone blocks with a rubble core. It survived to a maximum height of 4.06mOD* (3.61m above the base of the moat). The base of the wall was not observed. It measured 1.60m wide at the uppermost surviving level with a 4° batter (slope) on the moat-facing side. The wall was faced with limestone blocks measuring 0.71m x 0.42m x 0.24m. A layer of slate may have been used as a damp course, suggesting a high water level in the moat. Gun embrasures for canon added to the scarp at a later date were represented by a series of short regularly-spaced limestone walls. A total of nine gun embrasures were recorded during the investigations. A wide construction cut suggested the excavation of the moat and construction of Town Mount Bastion had taken place at the same time. On the western side of the bastion wall the cut had been infilled with deposits from the excavation of the moat which had probably been used to form the mount base of the bastion. This deposit appeared to have been reworked at a later date as it contained a clay tobacco pipe bowl dating to 1690-1700. The full extent of Town Mount Bastion was revealed, which was recorded for a length of 40m with no changes of orientation. The remains of the outer wall of the moat (counterscarp) were also recorded (see MPM2033). The bastion wall had been demolished to 4.06mOD* and the outer side robbed of its faced limestone to a level of 2.72mOD*. The depth of the demolition had probably been limited by the water level in the moat preventing access to the lower levels. 19th century finds, including an 1860 penny, were recovered from a compacted layer on the outer moat side of the scarp, trampled during demolition. The scarp wall had subsided slightly after the demolition. Thirty layers of infill were identified in the moat. Finds recovered from the various deposits included an 1860 penny, 1861 halfpenny, naval officers brass button, a mid-18th century clay tobacco pipe decorated with the Prince of Wales feathers, a lead musket ball, clay tobacco pipe dating to 1640-1660 and 17th century pottery. *Ordnance Datum - sea level [4]