Oblique aerial view of Carpow fort © RCAHMS
The new frontier arrangements were different from those in place during the first phases of Hadrian's Wall (Breeze 1982, 136-40). North of the Wall there were still three outpost forts to the west, at Birrens in SW Scotland, Netherby and Bewcastle in England. Now, however, there were complementary arrangements to the east. Forts remained in occupation along Dere Street running north from Hadrian's Wall at Portgate. These appear to have extended as far north as Newstead and may have included Cappuck, and perhaps Inveresk (Breeze, in press; Bishop 2004, 185). These most northerly forts appear to have been abandoned in about 180. It is likely that the frontier unrest of that time resulted in a reappraisal of Hadrian's Wall and the forts to its north. While these changes are often dated to the early third century and are regarded as a re-organisation of the northern frontier by the Emperor Caracalla, there are indications that some arrangements were already in place before that time, and it is possible therefore that they date to the post-180 settlement.
The post-180 arrangements included the basing of a thousand-strong mixed infantry and cavalry unit at Risingham and High Rochester on Dere Street with a couple of 'irregular' units. Scouts were probably also based at Netherby, called Castra Exploratorum, while a thousand-strong unit appears to have been at Bewcastle; Birrens was abandoned (Breeze 1982 , 136-140). The purpose of these arrangements was presumably to allow the army to maintain watch over the lands well to the north of Hadrian's Wall.
There is debate over whether some sites continued in occupation through this period (such as Cramond, where Holmes (2003, 154-5) argues the excavated evidence shows no clear break in occupation). It is also increasingly plausible that there may have been new foundations at this time. The legionary base at Carpow has long been seen as a Severan foundation, but reappraisal of both inscriptions and tiles from the site has been used to argue for suggested a Commodan foundation (RIB III, 3512-4; Warry 2006, 65-9). This would be, on current knowledge, a very isolated outpost, albeit one with good maritime connections, and if the interpretation is sustained raises questions about the nature of activity in Scotland at this time.
The sequences at the key sites of Cramond and Carpow, and the question of the end of Inveresk, need reappraisal as they are becoming critical to this period. A study of their pottery assemblages in the light of improved knowledge of the sequence on Hadrian's Wall at this date (from work at South Shields and Wallsend) would be very valuable.