Glevum, Lindum, Eboracum, and Corinium were all, perhaps, as large as Verulamium. Many of the ports on the south coast must have attained considerable size. But Britain, unlike Gaul, was not a province of great cities. Apart from resorts of merchants, such as London, the real centres of social life seem to have been the numerous villas. Nor, apart from prosperity at certain periods, can Britain ever have been a paying province. The number of troops permanently maintained there must have approached 40,000; while Severus was in the island there were probably 100,000; in 400 the Notitia shows over 50,000. Besides the expense of the army, there was that of the vast and ever-increasing bureaucracy, and of the maintenance of roads and military works. When the chief towns were walled we do not know. There is some reason to think that the fortification of London was begun by Severus I., but it is probable that most of the wall dates from a later period. The opinion of the authors, based upon careful examination of the quality of the work, is that it was constructed in great haste. The wall of Verulam is especially strong and massive, but whether it is so early as it is claimed to be is somewhat doubtful. Inscriptions are plentiful on the Wall of Severus, but not on those of the towns; and since the practice of commemorative inscriptions tended to die out in the fourth century, we are, perhaps, justified in supposing that the fortification of the towns was undertaken comparatively late. Everything is doubtful at present. We only know that the ‘departure of the Eagles’ left most of the British towns walled. Since at Silchester the wall crosses the ends of streets diagonally, the inference is that it was built at a late date to enclose only the closely inhabited area.