Hengist immediately sent representatives to Germany. He then took the hide of a bull and cut it into a single leather thong. With this thong he marked out a certain precipitous site which he had chosen with the greatest possible cunning. Inside the space which he had measured he began to build a fortress. Once this was completed, it took its name from the thong, since it had been measured out with one. This place, which we call Castrum Corrigie in Latin, was ever afterwards known as Kaercarrei in the Welsh tongue and as Thanceastre in Saxon. [VI.11]

Tatlock suggests that the location of Hengist's fortress must be CAISTOR in LINDSEY, a substantial Roman settlement.