The third-century ‘crisis’ (c. AD 250–70)

London’s port was abandoned in the mid-third century and its waterfront quays dismantled in changes that cast important new light on the problems of the third century. This chapter sets out the detail of the redundancy of London’s port and reviews arguments that might explain it. It does so by establishing a chronology that suggests that the port ceased to function effectively c. AD 255, and that the waterfront was crudely refashioned into a bank at some point in the 260s. This redundancy followed a rapid decline in the volume of goods being traded over longer-distances, and is argued to have been the consequence of a revised policy with regard to annona. The Thames may also have ceased to be tidal at this time, contributing to the redundancy of the port but not explaining the speed of its dereliction and destruction. Further light obtains from a study of the failure and abandonment of sites associated with Wealden iron production. An explanation is proposed: involving a loss of military manpower and naval capacity, possibly provoked by the epidemic of the 250s known as the plague of Cyprian and compounded by military failure and barbarian threat. Rome’s loss of control over its coastal waters and rising Frankish piracy at the time of the Gallic Empire might explain why ships ceased to dock at London’s quays, which were dismantled to defend the riverside.