This period ran from c.410 to 1066 AD. It could be split into two parts. The entry for the Anglo-Saxon Chronicle for 577 states "This year Cuthwin and Ceawlin fought with the Britons and they slew three kings - Commail, Condidan and Farinmail in the place that is called Deorham and took three cities, Gloucester, Cirencester, and Bath". Deorham is said to be modern Dyrham. However there is strong evidence for a 'Welsh' enclave surviving in South Gloucestershire until a much later date.
The Anglo-Saxon Chronicle and charters mention several places in South Gloucestershire as well as the murder of the Saxon King Edmund at Pucklechurch. There is also an analysis of the state of the region at the time of the Norman Conquest in the Domesday Book. Although some Saxon coins and pieces of jewellery have been found, we know perhaps less about this period than about others.
Recent excavations have recorded evidence for a sub-Roman cemetery near Filton.
Vikings
Although not very much in evidence in South Gloucestershire (so far) Viking raiders operated in the Bristol Channel for a number of years. The "Iron Age" fort at Oldbury-on-Severn has some similarities to sites in Scandinavia (trellegorge). Although larger than most of the Danish sites it is similar in size to the larges example at Aggersborg. There are diferences, but the suggestion is worthy of consideration.
Is our view of the vikings affected by what we see on TV?? Visit the associated web site to find out - perhaps?