Caersws derives its name from a traditional Queen Swsan, that carried on a war with a prince who reigned over a tribe on the south of the Severn. One day, seeing the enemy mustered on the Llandinam Hills, she crossed the river with her forces to give battle to the foe. The prince, occupying higher ground, was able to repel the attack; and the queen, seeing that her men were routed and in full flight, rode up to the prince and demanded to be put to death, that she might be buried in a great cairn beside her braves who had fallen. The prince replied that she was too gallant to be thus slain, and that he pardoned her; and further committed himself to her hands. Thenceforth their quarrels were fought out in private. The Roman castrum may still be traced--it covers about seven acres. Excavations made here have given up coins of Vespasian, Domitian, and of later emperors, also Samian ware. Roman soldiers must have been very regardless as to the condition of their pockets, for wherever they went they dropped their money. The plain would seem to have been a debatable ground from hoar antiquity, for every height about it is entrenched. It was one of the first obligations of a chief of a Celtic tribe to provide every married man who was subject to him with a farm, with seven acres of arable land, seven of pasture, seven of woodland, and a share in commons. Now as the tribe grew and multiplied he was put to great straits, and the only way out of his difficulties, where all the available land was appropriated, was for him to oust a neighbour from his territories. This obligation weighed on a chief to the eighth generation. Now suppose that a man started to found a tribe, and had three sons, and each of these sons had three, and all married, and in each generation had the same number. In the eighth, the tribe would consist of 2,673 marriageable men clamouring to be provided with farms of seven acres of arable, land, seven of forest, and seven of pasture. What could the chief do to satisfy them but lead them against a neighbour?