The characteristic earthwork of a probable Roman fort was first recognised from the air by Bob Jones, a pilot from Welshpool Airport with long experience of archaeological aerial reconnaissance. The potential significance of this discovery was obvious and a field visit was made to assess the monument on 17th October 2007 by Toby Driver, Jeffrey Davies, Hugh Toller, John Griffith Roberts and John Burman.

DESCRIPTION
The visit confirmed that the earthwork had all the attributes expected of a Roman fort. Its topographical position, bounded by streams on the north and south sides and the River Clywedog on the west and with excellent all-round views, is classic in terms of Roman military castramentation. Initially an alternative date for the earthwork could not be ruled out as it once lay within the lands of Cymer Abbey, and close to a recorded medieval township of Gwanas/Wonas (PRN 9859) as well as the presumed site of a medieval hospice or grange at Dol Yspytty (PRN 4135). Further investigation took place in February 2008. This comprised of a detailed earthwork survey of the above ground remains by the Royal Commission, a magnetometry survey by David Hopewell and John Burman, and a small scale excavation by John Griffith Roberts and Jeffrey Davies in the interior and across the inner bank on the east side, which produced no finds.

The results of this work have provided us with a more detailed picture of the monument and confirmed the initial interpretation of a Roman date. The enclosure is rectangular in shape, with rounded corners, enclosing an internal area 141m east to west by 124m north to south or 1.74 hectares (4.42 acres). It is defined by a double bank with a median ditch and has four entrances, one placed centrally in each side. The bank was some 3.5m wide with an inner and outer turf revetment with a mixed infill of soil, stone and dumped turfs. Although not examined the outer bank is of slighter character and appears to be a counterscarp. Along the western side, the rampart only partly survives along the line of a recently-dug drainage ditch bounded by a former hedge bank, and a recent plantation of deciduous trees. The northern rampart and north-east angle of the site have been lost to cultivation and were only confirmed by magnetometry; a steep scarp edge about 20m into this field suggests the former position of the destroyed rampart.
The fact that the magnetometry survey failed to provide any proof of permanent internal structures and that the enclosure is defined by a much slighter rampart than that of an auxiliary fort has led to its reclassification.

T. Driver, RCAHMW, 7th July 2008