(Re)dating Danebury hillfort and later prehistoric settlements in its environs: a Bayesian approach

The Iron Age (c800BC-AD50) was a key period of change, sitting between the earlier emergence of intensively farmed landscapes in the later Bronze Age and the incorporation of southern Britain into the Roman Empire. During the Iron Age, many key crafts and technologies were developed, using not just iron, but also other metals and materials, leading to innovations ranging from wheel-turned pottery to coinage. New forms of land division and settlement emerged, including its iconic hillforts.

Among the best known of these monuments is Danebury in Hampshire, where a 40-year research programme led by Sir Barry Cunliffe led to the excavation of over half the hillfort and 15 neighbouring settlements. No study of the period is complete without reference to Danebury and this hillfort dominates current interpretations of Iron Age societies in Britain.

Traditionally, Iron Age archaeologists relied on objects for dating, especially metal and pottery, but the dates were often inexact and compromised by sometimes tenuous links with the better-dated Mediterranean world. Over the last 50 years, earlier prehistory has turned to radiocarbon as an independent dating method, but this has been problematic for Iron Age studies due to the lack of precision, especially in the so-called ‘plateau’ between 800-400 BC - the very period when many hillforts were being built.

In the 1980s, a limited dating programme was undertaken for Danebury, but the introduction of accelerator mass spectrometry has allowed far smaller samples - even single cereal grains - to be more accurately and precisely dated. In combination with Bayesian statistical modelling of radiocarbon dates ordered by their stratigraphic position, it is now possible to date many archaeological events to a margin of decades not centuries, and potentially to surmount the problems that previously plagued radiocarbon dating of the Iron Age.

This collaborative project between archaeologists and scientists at the Universities of Leicester, Oxford and the Scottish Universities Environmental Research Centre, will build a new time-line for the Danebury area by reworking results from a 1980s dating programme and obtaining 300 new radiocarbon dates.

The results will provide a basis for critically reassessing the existing chronology for the southern British Iron Age and for rethinking social and cultural links between this region and the rest of Britain, as well as across the Channel. We know that many settlements around Danebury were abandoned and later reoccupied, but how these events relate to activity at the hillfort needs to be clarified. Through understanding when each site was constructed, remodelled and abandoned, we aim to develop fresh perspectives on social dynamics in the region.

Professor Colin Haselgrove   
University of Leicester

Professor Haselgrove was awarded a Leverhulme Trust Research Project Grant in March 2013.