After graduating with a degree in archaeology from Edinburgh University, Dr Caldwell spent 38 years working for the National Museums of Scotland. When he retired in February 2012 he was keeper of two of the five curatorial departments – Scotland and Europe, and Archaeology. Over the years he has tackled a broad range of archaeological and historical projects, mostly in Scotland but also in Turkey, Ghana and Chile.

He directed major research excavations at Finlaggan, Islay, the Centre of the Lordship of the Isles, and has maintained a strong interest in the history and archaeology of Argyll and the Western Isles. He has published over 100 academic and popular papers and articles and 7 books, including The Lewis Chessmen Unmasked and The Lewis Chessmen New Perspectives. Since 2014 Dr Caldwell has been President of the Society of Antiquaries of Scotland.