The Iron Age in Great Britain spanned from c. 800 BC until the Roman period in the 1st century AD. It followed the British Bronze Age and was marked by the use of iron for tools and weapons. The Iron Age saw the adoption of some elements of the Hallstatt and La Tène material cultures from mainland Europe, a marked increase in the building of hillforts, and the emergence of brochs in Iron Age Scotland. The British Iron Age excludes prehistoric Ireland, which had its own Iron Age cultures.
The protohistory of Britain begins during the late Iron Age. The earliest known account was by Greek geographer Pytheas, (c. 320 BC), who refers to the island as Albion, one of the Pretannikai nesoi (Pretannic isles), and describes its inhabitants as Keltoi (Celts). Most of the Iron Age inhabitants of Britain were Insular Celts and are referred to as Celtic Britons, as they spoke Celtic languages and had broadly Celtic cultural traits. The Britons, speakers of Common Brittonic, were made up of many tribes and kingdoms, and followed an ancient Celtic religion overseen by druids. Some of the southern tribes had links with Gaul and Belgica, and minted coins. There was also some Gallic and Belgic settlement in Britain. The Iron Age ended in most of Britain with the Roman conquest which began in 43 AD.
Etymology
Claudius Ptolemy described Britain at the beginning of Roman rule but incorporated material from earlier sources. Although the name "Pretanic Isles" had been known since the voyage of Pytheas, and "Britannia" was in use by Strabo and Pliny, Ptolemy used the earlier "Albion", which is known to have been used as early as the Massaliote Periplus.
The Iron Age appellation refers to the development of the technology of Ferrous metallurgy in Britain.
Periodisation
Over 100 large-scale excavations of Iron Age sites had taken place before 2005, dating from the 8th century BC to the 1st century AD and overlapping into the Bronze Age in the 8th century BC. Hundreds of radiocarbon dates have been acquired and have been calibrated on four different curves, the most precise being based on tree ring sequences.
The following scheme summarises a comparative chart presented in a 2005 book by Cunliffe. British artefacts were much later in adopting Continental styles such as the La Tène style of Celtic art.
The Iron Age has been further subdivided with the "Late Iron Age" in Britain showing developments of new types of pottery, possibly influenced by Roman or Gaulish cultures. The clearing of forests for cultivation of agricultural crops intensified and areas with heavier and damper soil were settled. Spelt (Triticum spelta) was planted in these areas like the Tees Lowlands and some parts of Northern England.
The end of the Iron Age extends into the very early Roman Empire under the theory that Romanisation required some time to take effect. In parts of Britain that were not Romanised, such as Scotland, the period is extended a little longer, say to the 5th century. Roman geographers like Ptolemy, Pliny and Strabo knew about the island.
Archaeological evidence
Attempts to understand the human behaviour of the period have traditionally focused on the geographic position of the islands and their landscape, along with the channels of influence coming from Continental Europe. Room 50 at the British Museum contains many of the best exhibits and is the source for the currently accepted interpretations of this period.
During the later Bronze Age, there are indications of new ideas influencing land use and settlement. Extensive field systems, now called Celtic fields, were being set out, and settlements were becoming more permanent and focused on better exploitation of the land. The central organisation to undertake that had been present since the Neolithic period but became targeted at economic and social goals, such as taming the landscape, rather than the building of large ceremonial structures like Stonehenge. Long ditches, some many miles in length, were dug with enclosures placed at their ends. Those are thought to indicate territorial borders and a desire to increase control over wide areas.
By the 8th century BC, there is increasing evidence of Great Britain becoming closely tied to Continental Europe, especially in Southern and Eastern Britain. New weapon types appeared with clear parallels to those on the Continent, such as the Carp's tongue sword, complex examples of which are found all over Atlantic Europe. Phoenician traders probably began visiting Great Britain in search of minerals around this time and brought with them goods from the Mediterranean. At the same time, Northern European artefact types reached Eastern Great Britain in large quantities from across the North Sea.
Defensive structures dating from this time are often impressive such as the brochs of Northern Scotland and the hill forts that dotted the rest of the islands. Some of the most well-known hill forts include Maiden Castle, Dorset; Cadbury Castle, Somerset; and Danebury, Hampshire. Hill forts first appeared in Wessex in the Late Bronze Age but became common only in the period between 550 and 400 BC. The earliest were of a simple univallate form and often connected with earlier enclosures attached to the long ditch systems. Few hill forts have been substantially excavated in the modern era, Danebury being a notable exception, with 49% of its total surface area studied. However, it appears that the "forts" were also used for domestic purposes, with examples of food storage, industry and occupation being found within their earthworks. On the other hand, they may have been occupied only intermittently, as it is difficult to reconcile permanently-occupied hill forts with the lowland farmsteads and their roundhouses found during the 20th century, such as at Little Woodbury and Rispain Camp. Many hill forts are not in fact "forts" at all and demonstrate little or no evidence of occupation.
The development of hill forts may have occurred from greater tensions that arose between the better-structured and more populous social groups. Alternatively, there are suggestions that in the latter phases of the Iron Age, the structures simply indicate a greater accumulation of wealth and a higher standard of living although any such shift is invisible in the archaeological record for the Middle Iron Age, when hill forts come into their own. In that regard, they may have served as wider centres used for markets and social contact. Either way, during the Roman occupation the evidence suggests that as defensive structures, they proved to be of little use against concerted Roman attack. Suetonius comments that Vespasian captured more than 20 "towns" during a campaign in the West Country in 43 AD, and there is some evidence of violence from the hill forts of Hod Hill and Maiden Castle in Dorset from this period. Some hill forts continued as settlements for the newly-conquered Britons. Some were also reused by later cultures, such as the Saxons in the early medieval period.
People
Britain, we are told, is inhabited by tribes which are autochthonous and preserve in their ways of living the ancient manner of life. They use chariots, for instance, in their wars, even as tradition tells us the old Greek heroes did in the Trojan War.
Most of the people of Iron Age Britain appear to have been Insular Celtic peoples, mainly Celtic Britons, while those in the north included the Caledonians. The Insular Celtic peoples are associated with Haplogroup R-L21, a sub-group of R-M269, which has its highest frequencies today among the Irish, Scots, Welsh, and Bretons.
The authors of a 2018 archaeogenetics study, Prof David Reich and Dr Carles Lalueza-Fox, proposed that the spread of Celtic language to Britain took place during the earlier Bronze Age, perhaps as early as the Bell Beaker migration at the start of the Bronze Age. In 2021, an archaeogenetics study (led by Nick Patterson, Michael Isakov, Thomas Booth, Lindsey Büster, and Claire-Elise Fischer) found that there was a gradual migration of people from Gaul during the Bronze Age, and that this led to a genetic change in the population of southern Britain (roughly England and Wales) at the end of the Bronze Age, between 1000 and 875 BC. Around half the ancestry of subsequent Iron Age people in that area were derived from these newcomers.
According to the authors of the 2021 study, "evidence suggests that, rather than a violent invasion or a single migratory event, the genetic structure of the population changed through sustained contacts between Britain and mainland Europe over several centuries, such as the movement of traders, intermarriage, and small scale movements of family groups". The authors describe this as a "plausible vector for the spread of early Celtic languages into Britain". There was much less migration into Britain during the Iron Age, so it is more likely that Britain became Celtic-speaking before then. Barry Cunliffe suggests that a branch of Celtic was already being spoken in Britain and that the late Bronze Age migration introduced the Brittonic branch.
The study also found that lactose tolerance rose swiftly in early Iron Age Britain, a thousand years before it became widespread in mainland Europe, which suggests that milk and dairy became a very important foodstuff in Britain at this time.
The Roman historian Tacitus suggested that the Britons were descended from people who had arrived from the Continent, and he compared the Caledonians (in modern-day Scotland) to Germanic peoples, the Silures of Southern Wales to Iberian settlers and the inhabitants of Southeastern Britannia to Gaulish tribes.
The Belgae arrived in southern Britain from the end of the 2nd century BC, as described in Caesar's Commentaries on the Gallic War. Such sudden events may be invisible in the archaeological record. In that case, it depends on the interpretation of Aylesford-Swarling pottery. Regardless of the "invasionist" vs. "diffusionist" debate, it is beyond dispute that exchanges with the Continent were a defining aspect of the British Iron Age. According to Caesar, the Britons further inland than the Belgae believed that they were indigenous.
Demography
The population of Britain increased significantly during the Iron Age probably to more than one million, partly due to improved barley and wheat and increased use of peas, beans and flax. Most were concentrated densely in the agricultural lands of the South. Settlement density and a land shortage may have contributed to rising tensions during the period. The average life expectancy at birth would have been around 25, but at the age of five, it would have been around 30. Those figures would be slightly lower for women, and slightly higher for men throughout the Middle Iron Age in most areas, on account of the high mortality rate of young women during childbirth; however, the average age for the two sexes would be roughly equal for the Late Iron Age. That interpretation depends on the view that warfare and social strife increased in the Late Iron Age, which seems to be fairly well attested in the archaeological record for Southern Britain at least.
Early in the Iron Age, the widespread Wessex pottery of Southern Britain, such as the type style from All Cannings Cross, may suggest a consolidated socio-economic group in the region. However, by 600 BC, that appears to have broken down into differing sub-groups with their own pottery styles. Between c. 400 and 100 BC, there is evidence of emerging regional identities and a significant population increase.
Iron Age beliefs in Britain
The Romans described a variety of deities worshipped by the people of Northwestern Europe. Barry Cunliffe perceives a division between one group of gods relating to masculinity, the sky and individual tribes and a second group of goddesses relating to associations with fertility, the earth and a universality that transcended tribal differences. Wells and springs had female, divine links exemplified by the goddess Sulis worshipped at Bath. In Agricola (2.21), Tacitus notes the similarity between both religious and ritual practices of the pre-Roman British and the Gauls.
Religious practices often involved the ritual slaughter of animals or the deposition of metalwork, especially war booty. Weapons and horse trappings have been found in the bog at Llyn Cerrig Bach on Anglesey and are interpreted as votive offerings cast into a lake. Numerous weapons have also been recovered from rivers, especially the Thames but also the Trent and Tyne. Some buried hoards of jewellery are interpreted as gifts to the earth gods.
Disused grain storage pits and the ends of ditches have also produced what appear to be deliberately-placed deposits, including a preference for burials of horses, dogs and ravens. The bodies were often mutilated, and some human finds at the bottom of pits, such as those found at Danebury, may have had a ritual aspect.