* This paper has benefited from the advice and criticism of Professor Alan Bowman, Dr. Jennifer Manley and the members of the Oxford University Ancient History Work in Progress Seminar. I am especially grateful to CQ's anonymous referee, whose perceptive comments prompted me to reconsider a number of key issues. Finally, I would like to thank Dr. Brian Jones, who provided much support and encouragement while supervising my research on the Severan period. All errors and omissions are my own responsibility.