Geophysics and Archaeological Excavation at Llys Caswallon, Llaneilian, Anglesey 2009-2010
Click on images to enlarge




Caswallon Lawhir was a semi-legendary ruler in Gwynedd, father of Maelgwn Gwynedd, with an obit. date of 534 AD. He is traditionally said to have given land to found Llaneilian clas church. The supposed site of his court, Llys Caswallon is marked on older maps such as the pre-Ordnance Survey Dawson 2-inch-to-the-mile manuscript map of 1816-20 (left, site marked red), the first edition Ordnance Survey map of Anglesey of circa 1840 and 19th century 6-inch-to-the-mile OS maps. The site marked on the latter is incorrect by some two hundred metres. The present geography of the area is shown in the aerial photograph at right (courtesy Google Maps, Google Earth). The name Caswallon is given to a modern house standing next to the road, showing that the tradition of the site was preserved long after all visible sign had disappeared. According to Angharad Llwyd's HIstory of Mona of 1833, stone was taken from the site to built the original of the house now on the site of this modern Caswallon villa.


There are few or no visible signs to indicate the location of the site of Llys Caswallon on the ground or from the air. However, after the rediscovery by geophysical survey it became possible with hindsight to trace the faint outlines of the greatly degraded bank defining the site's extent. Compare the aerial photograph with the geophysics plot at left below. Courtesy Google Earth, Google Maps





The initial geophysical survey was conducted in 2001 by Mr John Burman and T.P.T.Williams. This was designed to cover the 'official' site location and is the right-most rectangle above. Nothing except a possible trackway was found. In 2009 TPTW applied to Gwynedd Archaeological Trust for further survey by Mr David Hopewell which revealed the remaining areas shown to the left, including the rectangular bank-and-ditch enclosure containing signs of rectangular stone building foundations with evidence of burning.





After the initial geophysical survey of 2009 had located the site, a further high-resolution survey was commissioned by TPTW, resulting in the improved plot seen above. This enabled a trial excavation area to be targeted as shown by the white rectangle. This area was excavated in 2010. K. Laws and I.P. Brooks Engineering Archaeological Services Ltd.


Gwynedd Archaeological Trust conducted the 2009 geophysics magnetometer survey at Llys Caswallon

A general view of the excavation at an early stage, after de-turfing and looking NNW. Click on image to enlarge.


Section of clay-bonded stone wall at position 3 in the trench plan (right). Click on image to enlarge.

Section of clay-bonded stone wall at position 2 in the trench plan (right). Click on image to enlarge.

The areas between and to the south of the two wall sections are cobbled. Click on image to enlarge.


The area between the two wall sections is packed earth strewn with larger cobbles at the northern end. Are they fallen from the wall ?


The larger cobbles between the two walls seem poorly laid for a metalling - is a fall from the adjacent wall possible? Click on image to enlarge.



In contrast, the area south of both walls is well metalled including infill with smaller stones. Click on image to enlarge.






The ditch north of the bank, at position 1 (right) in section. Bank reveting stones have cascaded towards the ditch. Click on image to enlarge.



Trench plan showing the relative locations of the principal features. K. Laws and I.P. Brooks Engineering Archaeological Services Ltd. Click on image to enlarge.




Section plan of 5 metres of trench adjacent to bank and ditch showing the laid clay base on which the bank was constructed. K. Laws and I.P. Brooks Engineering Archaeological Services Ltd. Click on image to enlarge

View looking south showing fallen stones of bank revetment and the ditch in the foreground at position 1 of trench plan. Click on image to enlarge.


Rim sherd of 3rd or 4th century black burnished ware found on site. Click on image to enlarge.

Above and right are the reverse faces of the sherds. Click on image to enlarge.

Three sherds of degraded red ware were also found. Above are the outer faces. Click on image to enlarge.
















The inner fabric of the rimsherd.



In the 16th century the site was known as Buarth Caswallon as this old rent roll shows. Courtesy David Longley