Beyond the growing influence of the Catuvellauni during the first century BC were the Durotriges of Dorset. The tribe's territory extended into southern Wiltshire and southern Somerset, both to the north, where it met the borders of the Dobunni territory, and also edged into eastern Devon. To the east of the Durotriges were the Belgae, to the west were the Dumnonii along a line probably represented by the River Exe.
The Durotriges had no recognisable tribal centre, unless the mint at Hengistbury Head (on the border with the Atrebates/Belgae, near modern Christchurch) qualifies. This may also be the settlement called Dunium by the Roman-era geographer Ptolemy. Despite the lack of a recognisable centre, the Durotriges displayed an unusually dense volume of powerful hill forts, which was relatively unusual by the first century AD. These were to be the scene of a stubborn resistance to the Romans in AD 43. Maiden Castle is a finely preserved example of one of these hill forts. Following conquest, Durnovaria (Dorchester) and Lindinis (Ilchester) emerged as civitates.
Other References: Chris Rudd article on 2005 IOW hoard.