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Oystermouth Castle

Also known as, or recorded in historical documents as;
Ystum Llwynarth; Ostrelaf; Ostremew

In the community of Mumbles.
In the historic county of Glamorgan.
Modern authority of Swansea.
Preserved county of West Glamorgan.

OS Map Grid Reference: SS61328836
Latitude 51.57696° Longitude -4.00261°

Oystermouth Castle has been described as a certain Timber Castle, and also as a certain Masonry Castle.

There are major building remains.

This site is a scheduled monument protected by law.
This is a Grade 1 listed building protected by law*.


It is probable that William de Londres I founded the castle at Oystermouth in 1107 when Henry Beaumont conquered Gower. The primary castle of earth and timber was surmounted by a stone keep around 1138 and in the early thirteenth century an extended central block (incorporating the earlier keep) was added. The northwest block and part of the west range appear to have been added in the mid thirteenth century and in the late thirteenth century the gatehouse and curtain wall were constructed. In the early fourteenth century a chapel was added and other additions, including the southern offices and latrine turrets, were made before the end of the medieval period. There are traces of wall paintings in the southern recess of the chapel and on an area of plaster beneath the vault. These consist of a repetitive diamond pattern containing flowers and coats of arms. Traces of pigment have also been noted in the south-east angle of the recess. (Coflein)

Approximately 500m NW of Oystermouth church, prominently sited on high ground overlooking the village and Swansea Bay.
Oystermouth Castle was established c1107 by William de Londres. The first castle, probably of timber, is said to have been destroyed during the Welsh uprising of 1136, and was subsequently rebuilt by Maurice de Londres. The present keep is a partial survival of this second phase. The castle was again destroyed when it was captured by the Welsh in 1215 and held until 1220. Its re-acquisition by John de Braose, lord of Gower, probably saw rebuilding soon after, including the enlargement of the original keep into a more ambitious hall block. The NW and W blocks were added soon after and the castle was further strengthened by William de Braose, probably in the period 1256-66 when the present gatehouse and curtain walls were built following another assault. William clearly regarded it as his most impressive residence as in 1284 Edward I stayed there for 2 nights. The castle was attacked again during the rebellion of Rhys ap Meredudd in 1287. The addition of a chapel block is credited to the last of the de Braose family, Alina, who was resident 1327-31, but it may alternatively have been built by her son John, Lord Mowbray. Although Lord Mowbray was not permanently resident he was ordered to strengthen the defences in 1335. According to John Leland, by the 1530s the castle was ruinous. In the post-medieval period the late medieval service buildings were adapted as cottages, while the gatehouse was inhabited in the C18 and C19. The antiquary George Grant Francis undertook some restoration to the chapel block in the 1840s and other subsequent minor repairs. In 1927 the castle was sold by the Duke of Beaufort to the borough council of Swansea.
Ruined castle of rubble limestone, comprising a gatehouse at the S end, flanked by curtain walls at an angle to form a roughly triangular inner court with the keep and associated buildings on the N side. The Norman keep is centrally-placed on the N side of the court and occupies the highest ground. It has an added range on its N side, these 2 ranges forming the double-depth central block.The NW block abuts the central block while the W block is separated from the central block by a narrow passage. On the E side of the central block is the high chapel block of the C14. The 2-storey gatehouse is flanked by the curved walls of the former drum towers. Each tower has a blocked pointed doorway in the lower stage and beam sockets for an upper floor. The E curtain wall has a battered base and an added garderobe turret with return at the N end. Set back from the angle is the later chapel block, which has cusped lancets to the lower storeys and a 3-light window with intersecting tracery to the upper-storey chapel. The chapel block has an embattled parapet with arrow slits. In its N wall are two 2-light windows flanking a central square buttress. A further blocked lancet is lower R. The central block projects N, has a battered base and blocked E windows. In its N wall are putlogs and, in the lower storey, 3 narrow splayed lancets, with 3 wider lancets in the middle storey, while the upper storey is stepped in and has 2 windows. The adjoining NW block is obscured by vegetation but has a garderobe shaft to the centre, and in its W wall the head of a low arch is visible at ground level. In the W block is a shallow projecting garderobe turret to the NW end and a blocked window to its R. The W block has a string course below parapet level and putlogs. Small square-headed windows light the 2 cellars inside, beneath which the wall is battered. There is a butt joint between W block and the W curtain wall, which is faceted and has a single projecting garderobe turret added C14-15. The entrance passage of the gatehouse is tunnel-vaulted and retains a single portcullis slot. On the inner side the main gateway has a segmental arch in 3 orders that dies into the responds. Above is a formerly lintelled window. Segmental-headed doorways flanking the main gateway lead to steps down to the lower stages of the drum towers where there are blocked doorways. To the R of the R-hand doorway is an external stone stair to the upper storey. At the top of the stair is an arched doorway on the R to a small chamber with narrow window in its W side. The portcullis chamber has a window seat on the N side under a pointed rere arch. In the W wall is a fireplace with projecting segmental hood. Corbels supporting the former roof are retained. On the NE side is a short tunnel-vaulted passage to a newel stair, on the E side of the gatehouse, that leads up to the wall walk. The newel is partly renewed in concrete. The wall walk continues on both curtain walls. Both curtain walls retain evidence of 2-storey service buildings built against them in the late medieval period. On the E side, possibly a barracks, are 2 segmental-headed fireplaces, indicating a 2-storey building. On the W side the structure has 2 doorways to the court, although no jambs are now visible. Against the curtain wall are 2 segmental-headed fireplaces at ground floor level. In the NW gable end is a larger fireplace with projecting segmental head, indicating a kitchen. At the NW end is a small pointed doorway to a garderobe in the curtain wall. The central block comprises the basement of the mid C12 keep (although the openings are all later), which had a first-floor hall, extended in the early C13 by an additional gabled range on the N side to create a double-depth hall block. A storeyed porch on the W side of its front was added early C14 and is probably contemporary with the chapel block. The porch has a doorway with pointed arch reached up stone steps, leading to a tunnel-vaulted entrance vestibule which has a portcullis slot. The S wall of the keep has a round-headed arch of an inserted doorway later blocked with a narrow loop inserted inside it, and further R is a lancet window. The porch leads through a pointed-arch doorway to the basement below the first-floor hall. It has window seats in the S wall and in the E wall. In the N wall is a fireplace flanked by corbels of a former projecting hood. At the W end is a doorway to the later range added on the N side. Directly above it is another doorway. In the N and S walls are former beam sockets. Of the great hall on the first floor little detail is now visible. In the W wall are first-floor and gable windows, and beam sockets suggesting a screened passage and minstrel's gallery at this end. A projecting stair turret in the NW corner was an integral part of the C13 extension of the keep. It has a newel stair that is closed to the basement of the keep and N range, but communicates between the hall and a lower mural stair in the W wall of the added N range that leads down to a vaulted cellar beneath the N range. Around the newel stair is a mural passage communicating between the lower storey of the keep and the NW block. The N range of the central block has, in the S wall, a fireplace with a raked hood projecting on corbels. Window seats are in the E and N walls. Against the W wall are stone steps, inserted in the post-medieval period, to a tunnel-vaulted cellar. At the bottom of the steps the crown of an arch is visible in the N wall. The upper storey solar has 2 window seats in the N wall and a doorway at the W end, the embrasure of a window in the E wall. On the W side of the original keep is a guardroom, which is contemporary with the porch. It is 2-storey under a lean-to roof, the upper storey having been a room entered from the great hall. In the S wall facing the court is a pointed doorway with a draw bar socket. In the W wall are 2 slits and the embrasure of at least one window survives above. The narrow passage between central and W blocks has a segmental arch at the S end. The W block is built in 2 phases. The S range has 2 tunnel-vaulted cellars. In the southernmost cellar the vault partly obscures the head of a window, showing that the present vault is secondary. Stone steps against the E wall lead up to the ground floor. This has putlog holes visible in the N and S walls. In the W wall is a fireplace with corbels of a former hood. To the L of the fireplace at low level is the crown of a pointed arch. To the R of the fireplace is a low recess and further R a segmental-headed fireplace. The S wall has a large pointed-arched window. In the N wall a similar window was cut down to ground level to make a door when a further range was added on the N side. The batter at the base of the original N wall of the block is visible in the added N range. This added range is 3 storeys. The lower storey has, in the W wall a central window seat (the window is infilled) with fireplace to the L and a pointed doorway to the R leading to a garderobe. In the N wall is a doorway to the lower cellar of the NW block. In the middle storey W wall is a central window seat with fireplace to the L and doorway to the R, as in the lower storey. Access is gained through a pointed doorway in the E wall, to the R of which are a pointed window and stone steps to a segmental doorway into the lower storey. In the upper storey W wall is a central fireplace with a raked hood projecting on corbels. Attached to the E side of the range is a 2-storey projection with a roof of stone slabs, consisting of a cistern in the lower storey and 2 segmental-headed windows in the upper storey. The passage between central and W blocks leads to the NW block, which is 2 storeys above 2 superimposed vaulted cellars. Originally 2 storeys with one cellar, the block was heightened in the C14 to create a new upper storey while the original lower storey was converted to another cellar. The passage leads into the upper cellar through a pointed doorway with draw bar socket. Inside, the vault has an added central stone pillar. There are putlogs in N and S walls, 2 windows in the N wall and a blocked opening in the E wall. A garderobe in the NW corner has a narrow slit. The cellar does not extend the full length of the block as there are 2 cisterns at the W end. The lower storey of the NW block is reached by mural passage from the central block, or by a pointed doorway in the W wall of the range added on the N side of the central block. It has square-headed windows of the first phase at low level and the later square-headed windows, together with a fireplace in the S wall, at a higher level. Of the upper storey little survives. At the E end was a watchtower, the chamber of which retains a hooded fireplace, and from where steps lead up over the NW angle of the central block to the former parapet. The chapel block is on the E side of the central block and is of coursed limestone. It is 3 storeys and has projecting turrets on the SW, SE and NE angles, and central buttresses. The SW turret houses a newel stair. The upper-storey chapel has 2-light windows with hood moulds in its side walls. Inside, the basement has a window seat in the E wall, a wide segmental-headed fireplace in the N wall with a blocked window and seat to its L. In the S wall the main doorway is offset to the W side. At the E end is a doorway to a garderobe, on the W side a doorway to the stairway. The apartment in the middle storey has a window seat in the E wall. In the N wall is a doorway to the R leading to a garderobe in the NE turret, and a blocked window and seat to the L. The S wall has a fireplace with shallow cambered head, and to its R a window seat above the main lower-storey doorway. The upper storey was the chapel, which has two 2-light windows in the side walls and a 3-light E window. The chapel was entered from the great hall. The N and S walls have recesses said to have been confessionals. At the E end is a piscina with a cusped head. The E wall has corbels in the angles. A doorway in the SW angle leads to the mural stair which continues up to a gallery walk at eaves level. (Listed Building Report)

Oystermouth Castle is built on the western of two ridges overlooing the southern end of Swansea Bay. The castle consists of a central block set on the highest ground, to which additions have been made on the north-west and east. The central block contains the earliest work, and it appears that the southern half of this originally stood on its own while the other half was an early addition. The best preserved building in the castle is the one added to the south east corner of the central block. This contains traceried early 14th century windows and the largest chapel of any Glamorgan castle.
In the gatehouse, the entrance passage was flanked by twin round towers, but the outer half of each has been removed and the scars carefully patched. This is more likely to be the work of Cromwell than the hostilities of 1287. Outside the castle, north of the central block, there is a densely overgrown depression in the ground which may be the remains of a small bailey. (OS Record Card Glam Co Hist 3 1971 433-4 DB Hague) This castle occupies a dramatic hilltop location overlooking the broad sweep of Swansea bay towards Swansea, 6.5km t the NE. Originally the caput of a fief assigned to William de Londres, lord of Ogmore, at the conquest of Gower around 1107, it had reverted to the chief lords by the 13th century. Its subsequent tenure as a demesne castle inspired its later development, and in the late 13th and early 14th centuries, it appears to have supplanted Swansea Castle as the preferred residence of some lords of Gower. (Glamorgan-Gwent Archaeological Trust HER)
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This record last updated 20/04/2017 04:11:55