Iron Age Hillforts: The Fortified World Before the Roman Conquest

Iron Age Hillforts: The Fortified World Before the Roman Conquest

Iron Age hillforts are among the most dramatic and enduring monuments in the British landscape — earthwork fortifications built between roughly 800 BC and the Roman conquest of AD 43, crowning hilltops from Cornwall to the Scottish borders. More than 3,000 have been identified across Britain, yet despite their sheer number, these sites remain deeply misunderstood: they were not simply refuges in times of war, but complex centres of power, trade, and community life that defined the social world of prehistoric Britain.

What Is an Iron Age Hillfort?

The term "hillfort" covers an enormous variety of sites. At its simplest, a hillfort is a defended enclosure on elevated ground, protected by one or more circuits of ramparts — banks of earth, timber, or stone — and accompanying ditches. In practice, they range from modest enclosures of less than an acre to vast civic complexes covering dozens of acres, with multiple concentric defences, elaborately designed entrances, and evidence of dense internal occupation.

Construction began in the Late Bronze Age and accelerated dramatically through the Iron Age. Earlier hillforts often had a single rampart of earth with a timber palisade along the crest — a style archaeologists call dump construction. By the Middle Iron Age, from around 400 BC, many sites were rebuilt using glacis or box rampart styles, which created a steeper, more imposing face. Some ramparts were faced with dry stone walling or timber lacing. The scale of labour involved was extraordinary: estimates for the construction of Maiden Castle's later phases run to millions of person-hours.

The Social and Military Purpose of Hillforts

For much of the twentieth century, archaeologists assumed that hillforts were primarily military installations — places of refuge during inter-tribal warfare, occupied only in times of crisis. Extensive excavation has overturned this picture almost entirely.

The evidence from sites across southern Britain points instead to permanent or semi-permanent occupation: roundhouses arranged in rows, storage pits in their hundreds filled with grain, evidence of metalworking, weaving and specialist craft production, and finds of imported goods suggesting long-distance trade. Hillforts appear to have functioned as the political and economic capitals of their territories — the places where the powerful lived, where surplus was stored, where communal decisions were made, and where the bonds of tribal identity were expressed and reinforced.

This does not mean the defences were decorative. The ramparts of a major hillfort were an unambiguous statement of power, visible for miles across the landscape and requiring a substantial, organised population to build and maintain them. Conflict was real, as skeletal evidence of violent injury from multiple sites confirms. But the military function existed alongside — and perhaps in service of — the hillfort's role as a seat of authority.

Maiden Castle, Dorset: Britain's Greatest Hillfort

No site illustrates the scale and ambition of Iron Age hillfort construction better than Maiden Castle, which rises above the Dorset downland two miles south-west of Dorchester. Enclosing 47 acres within an immense system of multiple ramparts and deep ditches — in places four concentric banks stacked one behind another — Maiden Castle is the largest and most impressive Iron Age hillfort in Britain, and one of the most remarkable prehistoric monuments in Europe.

The site's history is long and layered. It began as a Neolithic causewayed enclosure around 3500 BC, was later bisected by a massive Neolithic bank barrow, and was then reoccupied and dramatically expanded during the Iron Age, with the great multi-vallate defences reaching their final form around 100–50 BC. The western and eastern entrances were elaborated into complex, winding approach routes that would have forced attackers into a killzone while making a dramatic impression on anyone arriving in peace.

Sir Mortimer Wheeler's famous excavations in the 1930s uncovered a war cemetery at the eastern entrance — dozens of skeletons showing evidence of violent death, some with Roman ballista bolts embedded in their bones. Wheeler interpreted this as direct evidence of the Roman assault on Maiden Castle during the campaigns of the future emperor Vespasian in AD 43–44. Later analysis has complicated this picture somewhat, suggesting the cemetery accumulated over a longer period, but the site's violent end at Roman hands is not seriously disputed. After the conquest, the population was relocated to the new Roman town of Durnovaria — modern Dorchester — and Maiden Castle was gradually abandoned.

Cadbury Castle, Somerset: The Hillfort and the Arthurian Legend

South Cadbury in Somerset is the location of Cadbury Castle, a hillfort that has attracted a quite different kind of attention — not for its size or its Roman destruction, but for its extraordinary post-Roman history and its persistent association with King Arthur's Camelot.

The site was occupied and defended throughout the Iron Age, with four lines of ramparts enclosing some 18 acres at its summit. Like Maiden Castle, it appears to have been attacked during the Roman conquest — a massacre deposit at the south-western gate includes the remains of men, women and children, alongside Roman military equipment. The settlement was subsequently dismantled.

What makes Cadbury Castle uniquely fascinating is what happened next. Excavations led by Leslie Alcock between 1966 and 1970 revealed that the summit was massively refortified in the late fifth or early sixth century AD — precisely the period in which a historical Arthur, if he existed, would have been active. A great hall was constructed within the refortified enclosure, and the scale of the works suggests a leader of exceptional resources and authority. The Arthurian identification, first recorded in the sixteenth century by the antiquary John Leland, cannot be proved — but archaeologically, Cadbury Castle is exactly the kind of site a post-Roman British warlord would have used as a stronghold.

Old Sarum, Wiltshire: Two Thousand Years of Continuous Power

Old Sarum, the great chalk hill overlooking the Avon valley north of Salisbury, is one of Britain's most instructive landscape monuments precisely because its story does not end with the Iron Age. The hillfort here — enclosing some 56 acres — was established in the Iron Age, and its commanding position above three river valleys made it a natural centre of power across the entire region.

The Romans recognised this immediately. After the conquest, Old Sarum became Sorviodunum, a Roman town positioned at the junction of major roads including the route that would become known as Ermine Street. After the Roman withdrawal, the site was reoccupied by Saxon settlers. The Normans then threw up a castle and a cathedral within the old earthwork circuit, and for two centuries Old Sarum was one of the most important fortified towns in England.

By the thirteenth century, conflicts between the castle garrison and the cathedral clergy, combined with practical problems of water supply on the exposed hilltop, led to the decision to build a new cathedral city in the valley below — and so Salisbury came into being, leaving Old Sarum to decay on its hill above. The hillfort's Iron Age earthworks survive beneath and around all of this later history, a reminder that the people who first chose this hill understood its strategic value as well as any Norman baron.

What Metal Detectorists Find Near Hillforts

The areas surrounding Iron Age hillforts are among the most productive zones for metal detecting finds of the period. Iron Age coinage — struck in gold, silver and bronze by tribal authorities across southern and eastern Britain — is frequently recovered in fields surrounding major hillforts. Terret rings, bridle fittings, dress fastenings and tools of iron and copper alloy all appear in the archaeological record. The concentration of activity around these sites means that associated farmsteads, trackways and field systems often extend considerable distances into the surrounding landscape.

Understanding what you've found near a potential hillfort — and what the surrounding landscape history might reveal about the site — requires cross-referencing multiple layers of historical evidence. Crop marks, documentary records, estate maps and local place-name evidence all contribute to a fuller picture, but searching and interpreting these sources is laborious and technically demanding work.

Aubrey Research automates this process, drawing on a wide range of historical records to generate a detailed landscape history for any location in Britain. You can see exactly what a finished report looks like at the sample report, or run your own search using the research tool.

Frequently Asked Questions

How many Iron Age hillforts are there in Britain? More than 3,000 Iron Age hillforts have been identified across Britain, though they vary enormously in size, complexity and period of use. The greatest concentrations are found in southern England, Wales and the Scottish borders.

**What is the largest