The late 3rd century and 4th centuries saw a series of crises in the Empire, including the breakaway Gallic Empire (of which Britain was a part), and raids by Saxon pirates, both of which led to the creation of the Saxon Shore forts along the East coast of Britain. The fort at Othona overlooking the confluence of the Blackwater and Colne estuaries, and two more at the mouth of the river into the colonia were built to protect the town. Balkerne Gate and Duncan's Gate were both blocked up in this period, with the later showing signs of being attacked. The extramural suburbs outside of Balkerne Gate had gone by 300 and were replaced by cultivation beds. The re-cutting of the town ditch in front of the newly blocked Balkerne Gate in 275-300 involved destroying the water pipes which entered the colonia through the gate. However a small portal in the gateway may have been opened up later. The town ditch began to silt up from c. 400 onwards. The troubles of the late 3rd century saw the burial of several coin hoards around the town, including a hoard of 1,247 coins found in a grey-ware pot at Hyderabad Barracks.