The excavations were undertaken by the Silchester Excavation Committee supported by donations from public and private bodies and from individuals and by permission of the Duke of Wellington, K.G., F.S.A. Their purpose was the investigation of (a) a previously unsuspected polygonal enclosure of about 85 acres, here named the Inner Earthwork, which lay partly inside and partly outside the line of the familiar Roman town wall; and (b) a western extension to the known line of the Outer Earthwork, which increased the size of this enclosure from about 213 to 233 acres. With the assistance of the Ordnance Survey, the aerial traces of these earthworks, first observed and recorded by Dr. J. K. St. Joseph, F.S.A., were confirmed and extended by field-work and excavation, and have been planned as appears on pl. I.
The excavations showed that the Inner Earthwork was a defence of Gaulish ‘Fécamp’ type, and that it was erected, on the south, over an area of late pre-Roman occupation, the first clearly identified at Calleva Atrebatum, but one with strong ‘Catuvellaunian’ influences in its pottery-series. It is claimed that the Inner Earthwork was constructed by the client King Cogidubnus in or shortly after A.D. 43–4, as the defence of this, the most important settlement in the north-west of his dominions. It is further suggested that the Inner Earthwork was replaced by the Outer Earthwork also during the reign of Cogidubnus.
The excursus attempts to collate with the results of excavation the earlier discoveries of pre-Conquest material. The total evidence is finally related to the Belgico-Roman topography of Silchester and its neighbourhood, within the historical framework of the century and a half which separated the arrival of the earliest Belgic immigrants in the region from the death of Cogidubnus and the consequent emergence of the Roman Civitas Atrebatum.