Between A.D. 286 and 296, the Gallo-Roman military commander Carausius and his successor Allectus ruled Roman Britain, forming a renegade government there that threatened the stability of the Roman Empire. Constantius Chlorus eventually suppressed this separatist regime, and his success paved the way for his son Constantine to use Britain as the base for his own bid for imperial recognition. Using literary, archaeological, and numismatic evidence, P.J. Casey brilliantly pieces together this little-known but extraordinary episode in the history of Roman Britain. Casey sets out the Continental and British background to the revolt, which he closely dates and, contrary to current published wisdom, locates initially in Gaul. He finds that Britain's independence was based on naval power-the first time that insular sea power played a major part in British history. He describes how Carausius and Allectus controlled the sea-lanes of the English Channel and the North Sea, maintaining what was probably the most effective naval force in the Roman world after serious naval warfare ceased in the reign of Augustus. He reviews the marine technology of the period and outlines the strategies of Roman coastal protection. He concludes by considering how Carausius was depicted by writers from the medieval period onward, in particular assessing the use of Carausius and Allectus as historical icons in periods of national crisis in British history.