This is the third of three monographs that present the results of archaeological investigations carried out by Northern Archaeological Associates during Highways Englands upgrading of 19km of the A1 dual carriageway to motorway status between Leeming and Barton in North Yorkshire from 2013-17. The first monograph concentrates on human burials, and the second upon the Late Iron Age and Early Roman transition period at Scotch Corner, and this work is focused principally on the Roman period. This monograph explores the research theme Establishment, Consolidation and Retreat, along with a wide range of attendant research questions concerning the evidence from Cataractonium and its hinterland. The monograph is released in two parts and is released with 24 appendices.