CASTELL ARNALLT A TOPOGRAPHICAL SURVEY by NEIL PHILLIPS Castell Arnallt is the name given to a large, oblong mound lying in pasture land by the side of the River Usk, some four miles east south east of Abergavenny, SO 320 100. Its longest axis, east to west, measures just over 150m with its north south axis, 78m. It is situated on ground sloping gently from north-east to south-west, and as such its height varies being four metres on the north and eight metres on the south. The long axis can be divided into two areas: the eastern half being a flat-topped plateau some four metres higher than the western half, which takes the form of an elongated spur. Castell Arnallt is included in a report of circa 1767 on the lordship of Abergavenny' and is considered by Bradney2 as having belonged to Seisyll ap Dyfnwal, the Welsh leader in Gwent Uwchcoed.3 Henry II had created Seisyll Lord of Over Gwent with the honour of Abergavenny castle in return for releasing a hostage, Hugh de Beauchamp. As part of the peace proceedings between The Lord Rhys and Henry II, Seisyll, The Lord Rhys's brother in law, was persuaded to give the Honour of Abergavenny Castle to William de Braose.4 The infamous massacre at Abergavenny castle on Christmas Day 1175 records not only the end of Seisyll and his son but also later in the day the murder of his family and the destruction of his home, Castell Amallt,5 There is no known reuse of the site since 1175 other than for agricultural purposes. The site has not been excavated and has been scheduled since 1947. The topographical survey was carried out by the author as part of his Ph.D research at UWCN. The survey was made with a Topcon GTS 212 total station and results processed by Civilcad 5.5 software. The resistivity survey was carried out using a Geoscan RM 15 resistivity meter fitted with 0.5m array. The Geoscan used 20m. grid squares arranged as seen in fig. 1, readings therefore, amount to 400 per 20m square. Fig. 2 shows the geoplot interpretation with the contour plot of the site. Shaded areas a e show up as high resistance curvilinear features that follow the shape of the hill. Surface stone is evident in some of these areas due to slope erosion. It is proposed therefore, that these areas form an inner wall or palisade base. Between d and c there is a large gap, which, in combination with the colour layout and visible surface features, was interpreted as an entrance. Area f appears to be part of the entrance feature but the geoplot and surface features suggest that there is a gap between f, d, and e. Shaded areas g, h, k, m, n, appear also to follow the shape of the hill in the same way as a e, and so it is reasonable to interpret them as a second ring of wall or