ABSTRACT
The different kinds of evidence, their relative degrees of importance and the techniques of study and interpretation have been explained in the first and companion volume on the Invasion, and so will not be repeated here. But an exception must be made to acknowledge the outstanding contribution of Professor St Joseph, who has been flying over Wales and its Marches since 1945, and has published his results in regular summaries in JRS.1 The enormous addition to knowledge can be seen on his map of the Marches of 19732 on which are plotted 33 concentrations of military sites of forts and campaign camps. Arnold Baker and Professor Barri Jones have also done notable work, the former especially in the Wroxeter area. Without the devoted services of these flyers, the following section could not have been attempted.
