These excavations by St John O'Neil, who was the Inspector of Ancient Monuments in Wales, were carried out to a high standard. Five sections were cut across the various ramparts and three area excavations were opened. This was following the most recent excavation practices developed by
Mortimer Wheeler for his excavations at the hillfort at
Maiden Castle in
Dorset. O’Neill was able to define the earliest phase of the hillfort as smaller enclosure measuring 170 m by 80 m (1.2 hectares), with a gateway to the south, and defended with two rows of timber
palisades. This enclosure stands on the highest area of the hill and contains a small mound which may have been a
Bronze Age round barrow. Under the southern gate of this enclosure evidence for earlier
Neolithic occupation was found. This enclosure was then modified by a box framed timber
rampart, with an extension to the north-west and a
barbican added to the south gateway. The inner area of the enclosure contained a number of rectangular "four-poster" structures, which are now interpreted as the supports for wooden framed granaries. The next phase was to greatly enlarge the hillfort, with timber laced ramparts, which took in much of the slope of the hill to the north-west, towards the river Severn. The hillfort now measured 300 m by 200 m, and covered 4.4 hectares. The existing banks of this enclosure still in places stand to between 3 m and 8 m in height. A large "annexe" area was added to the south-west gateway of this enclosure which may have acted as a barbican. The defences of the larger hillfort appear to have fallen into decay, and at some point, possibly at the time of the
Roman conquest of Britain, were refurbished with a simple earthen bank. ==Interpretation==