 The fort, built in the 230s, became later part of the Saxon Shore fortification system.It was built to guard the Wash approaches and is of a typical rectangular "castrum" layout.According to the 4th-century document "Notitia Dignitatum", the fort was garrisoned by the "Equites Dalmatae Brandodunenses" ("Dalmatian cavalry of Bran[d]odunum"), although a tile found on the site stamped "Cohors I Aquitanorum" suggests that its original garrison was the "First cohort from Aquitania".