Such was this formidable barrier in its complete state; but it is not likely that it owed its entire construction to Lollius Urbicus. His work appears to have been limited to what was constructed of turf, and consisted probably only of the earthen rampart itself. Few probably, if any, of the principal ‘castella’ formed part of the original construction, as their remains indicate a more elaborate foundation. Numerous inscriptions have been found along the course of the wall, which show that the ‘vallum,’ as it is termed in these inscriptions, had been constructed by the second, the sixth, and the twentieth legions, or rather by their vexillations. The first and last of these legions had been in Britain since the time of Claudius; the sixth was brought into the island by Hadrian. The inscriptions connect the work with the name of Antoninus, and in one that of Lollius Urbicus has been found. [Sidenote: A.D. 162. Attempt on the province by the natives.] This great work, guarded as it was by a powerful body of Roman troops, seems to have effectually protected the Roman province in its increased extent during the remainder of the reign of Antoninus. But the first year of a new emperor was, as usual, marked in Britain by an attempt upon the province by the northern tribes, and Calphurnius Agricola was sent to Britain to quell them. This was in the year 162.[72] [Sidenote: A.D. 182. Formidable irruption of tribes north of wall repelled by Marcellus Ulpius.] In the commencement of the reign of Commodus, twenty years later, the irruption was of a more formidable character. The nations on the north of the wall succeeded in breaking through that great barrier, slew the commander with a number of the soldiers who guarded it, and spread devastation over the neighbouring part of the province. The war created great alarm at Rome, and Marcellus Ulpius was sent by Commodus against them,—a general whose character, as drawn by Dio Cassius, peculiarly fitted him for the task, and he appears to have succeeded in repelling the invading tribes, and terminating the war two years later.[73]