Thangcaster, Thong Castle
The castle known as Kaercarrei by the Britons. It was later called Vancaster or Lancaster.
The Saxon leader Hengist built it as a stronghold in Britain while he was on friendly terms with Vortigern. According to Geoffrey, it was so named because Hengist measured out the foundation of the castle with a leather thong.
The town is probably Caistor, located in Lincolnshire, England. The name “Caistor” suggests a connection to its Roman origins, as ceaster is a common element in place names derived from Latin castra, meaning “fort” or “camp.”
See also
Siege of Thong Castle | The Legend of King Arthur
Sources
Historia Regum Britanniae | Geoffrey of Monmouth, c. 1138
Roman de Brut | Wace, c. 1155