It is Cadbury's later history and folklore that give it Arthurian significance. It is one of the several locations of "Arthur's Cave" - a legend that states once a year a pair of magical gates open in the hillside and Arthur can be seen sleeping within, awaiting Britain's hour of greatest need. There are also Arthurian ghost stories told in the region. Tudor writer John Leland referred to the hill as Camelot in 1542. He stated this was local belief and a local tradition is likely. Indeed, while the Camelot of romance never existed, Cadbury may have been the headquarters of one of the Arthurian prototypes or at least a king from his time period.
Major excavations from 1966-70 uncovered some real possibilities. Cadbury was evidently re-inhabited in the late 5th to early 6th centuries. Large scale construction was begun. A dry-stone wall sixteen feet thick was found embedded in the topmost earthen bank. This was bound by a framework of timber and had a total perimeter of 3/4 of a mile. There was a great hall on the plateau and a gatehouse that protected the entrance.
Other hill-forts were reclaimed at this time but none on the scale of Cadbury. The stone and timber defense system is found nowhere else in England or Wales and Scottish examples are much smaller with no gatehouse.
Because of the manpower and labor required to build these fortifications, it is generally held that this was the seat of a king, maybe a "High King," with wealth and resources unmatched in the rest of Britain. Without any documents or further evidence, not much more can be said that isn't speculation.