id: sig-20260722-report-gm007
site_id: gb-mumbles-oystermouth
attribute: designation_report
value: 'Reference Number

  GM007

  Name

  Oystermouth Castle

  Date of Designation

  Status

  Designated

  Unitary Authority

  Swansea

  Community

  Mumbles

  Easting

  261325

  Northing

  188367

  Broad Class

  Defence

  Site Type

  Castle

  Period

  Medieval

  The monument consists of the remains of a castle, dating to the medieval period. Oystermouth
  Castle was established c. 1107 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 north-west
  and west 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 18th and 19th centuries. The antiquary George Grant Francis undertook some restoration
  to the chapel block in the 1840s and other subsequent minor repairs.

  The monument is of national importance for its potential to enhance our knowledge of medieval
  defensive practices. The monument is well-preserved and an important relic of the medieval
  landscape. It retains significant archaeological potential, with a strong probability of
  the presence of both structural evidence and intact associated deposits.

  The scheduled area comprises the remains described and areas around them within which related
  evidence may be expected to survive.'
source_url: http://cadwpublic-api.azurewebsites.net/reports/sam/FullReport?lang=en&id=2860
source_title: Scheduled Monument Full Report — Oystermouth Castle
publisher: Cadw
observed_date: '2026-07-22'
collected_by: scripts/build_assessment_batch.py
confidence: high
notes: The designation text. Assess the six bands against THIS evidence only; omit any band
  it does not speak to.