We are now familiar with the Three Age System, the archaeological partitioning of the past into Stone Age, Bronze Age, and Iron Age. This division, which amounted at the time to a major scientific revolution, was conceived in Denmark in the 1830s. Peter Rowley-Conwy investigates the reasons why the Three Age system was adopted without demur in Scandinavian archaeological circles, yet was the subject of a bitter and long-drawn-out contest in Britain and Ireland, up to the 1870s.