Radiocarbon dating was long neglected in Iron Age research, with dates on the 'Hallstatt plateau' (800-400 BC) considered too broad to be useful compared to artefact typo-chronologies. Such views are now untenable. Around fifty British Iron Age settlements and cemeteries have been dated using Bayesian methodologies, yielding two important general results: (1) typological dating produces sequences that are regularly too late; and (2) many phenomena, from chariot burials to settlement shifts, represent brief horizons, rather than being long lived. Drawing on a selection of studies, this article explores the impact of Bayesian modelling on British Iron Age studies. It highlights potential pitfalls and issues that must be considered when dating the period, illustrates some major successes and looks to the future.