If we could believe certain chroniclers, the history of Shrewsbury would begin more than four hundred years before the Christian era; but we can hardly doubt that the town existed in the days of the Romans. Towards the close of the sixth century English invaders came marauding up the valley of the Severn, and destroyed the old city of Wroxeter. For a time the fugitives found a refuge in the fortified palace of the Princes of Powis, which then stood on the headland now occupied by Shrewsbury; but before long that stronghold also became a prey to the plunderers, and the Britons were forced to seek safety among the fastnesses of Wales. Then Pengwern, as it had been called, became Scrobesbyrig--"the burgh of bushes"--from which obviously it has obtained its present name. Before very long its importance as a frontier town was fully recognised, but at first it remained small--probably because it was too near Wales for merchants or for men of peace--so that at the date of Domesday Book, though it had four churches, it contained only 252 houses. The castle was built a few years later by Roger de Montgomery, a Norman earl, and a gateway leading to the inner court is a relic of his work. The enclosing wall of the town was completed in the reign of Henry III. This follows, as far as possible, the line of the ancient river-cliff, which on the southward side is parted from the Severn by a strip of level land. Portions of this wall still remain, and it can be traced more or less perfectly along the southern and eastern sides.