The site was abandonned during part of the bronze age with the present fortification and settlement beginning around 600 BC. It was at the centre of the territory claimed by the Durotriges tribe at the time of the Roman conquest.

The first stage enclosed about 16 acres (6 hectares) and was expanded at aournd 450BC to cover 47 acres (19 hectares) nearly trippling in size. At this point it was the largest hillfort in Britain. There is some evidence that its population was declining by 100BC and gravitating to the eastern end of the site. Further east amongst the 'Belgic' tribes in britain hillforts were being abandonned in favour of undefended lowland settlements in some places, and it may be that this was beginning to happen in the area between Mai Dun and modern Dorchester (Roman Durnovaria). It is not yet certain that the settlement on the plain began before the Roman conquest.

Mai Dun' defences had been strengthend or at least 'advertised' by multiple concentric banks and ditches in concentric rings around the hill. On the south side there are four banks, all impressively sttep and high even after 2000 years of erosion. The principal entriy points are at the east and west (the narrow ends of the hill); the east gate in particular has been engineered to force incomers to meaner from side to side by two 'bastions' placed between the gaps in the banks ringing the fort. This would expose any attackers to missile fire from the defenders. An excavation just inside the east gate uncovered a pit containing about 20000 pebbles chosen for their shape as suitable amunition for hand slings. This amunition store has been dated to the first century AD.

Two trade systems existed between Britain and the continent, a western system between southwest Britain and Armorica (and Spain) and a southeast system between Kent and Belgic Gaul. This is perhaps an indication that the Durotriges did not regard themselves as a Belgic tribe. Cross channel influences of the disruptions in Gaul arising from Germanic and Latin Pressure after 100BC lead to a consolidation of political groupings in southern Britain.

In the Southwest this resulted in the fortifications of existing hillforts being enhanced and larger more centralised groupings developing. The key point in the Southwest was the Durotrigan port at Hengistbury Head, where metal was worked and exchanged for luxury pottery, metalwork and wine from Armorican traders. Mai Dun and Danebury hillforts were perhaps more regional or seasonal centres at this time though important in controlling a hinterland and the overland trade routes.

The Southeastern Britons were sending raw materials slaves and mercenaries to Belgic Gaul at this time, and some leaders amongst the Continental Belgae made plundering raids in the Southeast ultimatly acquiring local follower, and tributary british communities. The Suessionian king Diviciacus was said to had had extensive holdings in Britain in the 70s BC. At this time many southeatsern nobles began striking coinage after the current continental Belgic fashion. Durotrigan coinage however kept to the native British style.

Sources: Doman Dorset, Bill Putnam.- 2007.
The ancient celts, Barry Cunliffe, 1997.
Historical atlas of Britain, Malcolm Falkus, John Gillingham, 1981