Julian specialises in the archaeology of Anglo-Saxon and Viking Age England, especially mortuary behaviour and settlement evolution. He has directed excavations of Anglo-Saxon and Anglo-Scandinavian settlements at Cottam, Cowlam, Burdale, and Wharram Percy. He has also excavated the only Viking cremation cemetery in the British Isles at Heath Wood, Ingleby. He directed an AHRC-funded research project investigating the Viking and Anglo-Saxon Landscape and Economy of England, and he is currently  in collaboration with Professor Dawn Hadley to investigate the winter camp of the Viking Great Army at Torksey.

Julian is also a leading expert on computer applications in archaeology and has authored and edited numerous books and papers on computer applications. He is Co-Director of Internet Archaeology, an electronic journal developed in York, and Director of the Archaeology Data Service, the national digital data archive for archaeological research.