Fonmon Castle

Has been described as a Certain Masonry Castle

There are masonry ruins/remnants remains

NameFonmon Castle
Alternative Names
Historic CountryGlamorgan
Modern AuthorityVale of Glamorgan
1974 AuthoritySouth Glamorgan

A mansion, incorporating substantial elements of a medieval masonry castle, including a late C12 keep and work of C13-C14. The castle was much added to in C16, with a great refurbishment, c.1760, and minor modern additions and alterations. (source: RCAHMW 2000, 147-165) J.Wiles 27.01.03 (Coflein)

It is speculated that a timber castle was built on this site soon after the Norman Conquest of South Wales, the first stone building added in about 1200. This would have adjoined or been within the timber enclosure, but there is little physical evidence, apart from the changes in level in the gardens and outworks and the 'Watchtower'. The first surviving stone build is well away from the edge of the ravine, and is the section on the left of the entrance court, running east-west and containing the Drawing Room in what was the first floor hall of the castle. This section has the thickest walls of the present building, but since it is small, approx. 8m x 13m, it is possibly only a part of what was in use until more of the stone castle was built. This was the east curtain which extended the existing range to the edge of the precipice and then turned the south-east corner to include the south range. The rooms within the east curtain, now the Stairhall, appear to have been created by Colonel Jones in the 1660s, with both the west wall and the roof dating from then, but it would probably have had a building against it previously. The thickest section of these walls are along the ravine edge where attack would be least likely, so the more vulnerable south and west approaches to the castle must have been defended in some further way not now apparent. This second phase of stonework, with both square and rounded towers, must be from fairly early in the C13, beforr the more vulnerable square corner tower fell from favour. It was probably built by the St. John family, who were the owners later in the Middle Ages and until 1656

The open quadrangular form of the C13 castle with apartments set against a curtain wall would strongly suggest that it was intended to be a complete quadrangle, but this appears never to have happened. The next major addition seems to be a short, north wing built in the C16 over a characteristic barrel-vaulted semi-basement. The castle was undamaged in the Civil War, the St. John family being Parliamentarians, but they later fell on bad times financially and in 1656 sold their Glamorgan estate to Colonel Philip Jones whose successors still own it today. The Colonel appears to have been responsible for the addition of the double depth wing on the north side of the castle and the rooms of the east range, but some of the internal decoration may date from after his death in 1674 and be attributable to Oliver Jones 1678-85. The next major addition, representing its present internal character, was the work of Robert Jones III. He married Jane Seys of Boverton in 1762 and began the castle improvements by employing Thomas Paty of Bristol. This firm had done similar makeovers to houses such as the C16 Stoke Park north of Bristol in 1760-4, and they supplied the overall battlements and render to enhance the castle look while at the same time putting in a regular display of sash windows to improve the light, and remodelled the interior for comfort and elegance. This involved breaking through walls to increase the size of rooms, thus forming the Stairhall and the Drawing Room, and making further improvements to the service end following what had already been achieved in the late C17. The C19 saw the estate in decline and little was done to the castle except for the addition of the entrance porch and the extension to the south wing between 1840 and 1878; the extension appears to be shown on the Tithe Map of 1841. There is a possibility that the C19 alterations may have been more considerable, with the mid C18 pastiche on the staircase and in the Dining Room dating to this time for example, but this is uncertain. The castle passed by marriage to Sir Seymour Boothby in 1917 and his grandson still lives there. (Source; Cadw listing database) S Fielding RCAHMW 04/12/2006 (Coflein)

Fonmon Castle is in good condition. The walls are castellated, but the surface have been roughcast. There is no trace of any earthworks around the castle. The castle is a substantial mansion situated on the western lip of a steep ravine below the gardens and castle in which the Fonmon Brook runs northwards to join the Kenson river. Castellation, rendering and Georgian sash windows give the castle a uniform appearance, but they mask several building phases from the medieval period onwards. It is a 2 and 3-storeyed building orientated N-S, with a small entrance court, open to the west, at the south end of the west side. The earliest part of the building is a rectangular 12th century keep which lies along the north side of the court, orientated E-W. (Glamorgan-Gwent Archaeological Trust HER)

Not scheduled

This is a Grade 1 listed building protected by law

Historic Wales CADW listed database record number
The National Monument Record (Coflein) number(s)
County Historic Environment Record
OS Map Grid ReferenceST047680
HyperLink HyperLink HyperLink

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  • Morgan, Gerald, 2008, Castles in Wales: A Handbook (Talybont: Y Lolfa Cyf.) p. 144-5
  • < >RCAHMW, 2000, An Inventory of Ancient Monuments in Glamorgan Vol. 3 Part 1b: The Later Castles (London: HMSO) < > p. 147-165
  • Pettifer, Adrian, 2000, Welsh Castles, A Guide by Counties (Boydell Press) p. 96
  • Reid, Alan, 1998, Castles of Wales (John Jones Publishing) p. 84
  • Newman, J., 1995, Buildings of Wales: Glamorgan (Yale University Press) p. 350-1
  • Salter, Mike, 1991, The Castles of Gwent, Glamorgan and Gower (Malvern) p. 51
  • Davis, Paul R., 1983, Castles of Glamorgan (Alun Books) p. 39
  • King, D.J.C., 1983, Castellarium Anglicanum (London: Kraus) Vol. 1 p. 163-4
  • Fry, P.S., 1980, Castles of the British Isles (David and Charles) p. 355
  • Moore, P., 1978, 2edn (1edn 1976), Fonmon Castle South Glamorgan: a Residence Occupied since the Thirteenth Century (Glamorgan Archives Joint Committee, Cardiff)
  • Renn, D.F., 1973 (2 edn.), Norman Castles of Britain (London: John Baker) p. 190
  • Hague, D.B., 1971, in Pugh, T.B. (ed), Glamorgan County History Vol. 3 The Middle Ages (Cardiff) p. 440
  • Williams, Stewart, 1959, 'Fonmon Castle' in Williams, Stewart (ed), History on My Doorstep (Barry)
  • Clark, G.T., 1884, Mediaeval Military Architecture in England  (Wyman and Sons) Vol. 2 p. 49-50 (reprint of 1861 article) online copy
  • Lewis, Samual, 1849, A Topographical Dictionary of Wales online copy
  • Homfray, Jeston, 1828, The Castles of the Lordship of Glamorgan (Cardiff) p. 41 and plate


  • Toulmin-Smith, Lucy (ed), 1906, Leland's Itinerary in Wales  (Bell and Sons; London) p. 24 online copy


  • Thomas, Howard J., 1999, 'The manor and castle of Fonmon' Morgannwg Vol. 43 p. 63-82 [online copy > ]
  • Spurgeon, Jack, 1987, 'The Castles of Glamorgan' Château Gaillard Vol. 13 p. 209n, 222
  • Hogg, A.H.A. and King, D.J.C., 1967, 'Masonry castles in Wales and the Marches: a list' Archaeologia Cambrensis Vol. 116 p. 71-132
  • Oswald, 1949, Country Life Vol. 105, p. 606-9, 670-3, 734-7
  • Jones, 1882, Cardiff Naturalists' Society Vol. 14 p. 44-9
  • Clark, G.T., 1861, 'Some Account of the Parish of Penmark' Archaeologia Cambrensis Vol. 16 p. 8-9

Guide Books

  • Patricia Moore, 1985 (3 edn), Fonmon Castle (Glamorgan Archive Services)