Dr John Barber is a distinguished archaeologist and founder of AOC Archaeology Ltd, where he was Managing Director until 2011. He is particularly interested in the architecture and engineering aspects of prehistoric structures – how they were built, how some were amended over time, and what happens when they collapse or decay. He has experimentally built, and pulled down, parts of three chamber tombs, and has recently been involved in the excavation of five brochs. In 2018, he presented the prestigious series of Rhind lectures to the Society of Antiquaries of Scotland, ‘Drystone technologies: Neolithic tensions and Iron Age compressions’ ((1) Rhind Lectures 2018 – YouTube). In this lecture, delivered as part of the European Heritage Days series in 2021, he discusses the impressive Iron Age broch at Dun Carloway on the Island of Lewis.