The problem of the duration of the first Roman occupation of Scotland is an interesting and important one, and it has been the subject of considerable discussion since the excavation of Newstead added the evidence of archaeology to that of the scanty literary sources. There can be no doubt that, by the time that Hadrian's Wall was planned, Agricola's conquests north of Cheviot had been relinquished by the Romans, but it is not definitely known at what date after his recall, late in the year A.D. 84, the withdrawal took place. There are four emperors under whom the change of frontier policy thus effected may have occurred—Domitian, Nerva, Trajan and Hadrian. The latter's evacuation of most of Trajan's Eastern acquisitions seemed, at one time, to qualify him as the author of a similar limitation of the Empire's extent in Britain.
