The creation of the burhs was a well ordered programme which obviously required central planning coupled with expert knowledge of existing conditions.

It is likely that the construction of the burhs fell into three main phases:

Phase 1

The use of existing sites such as towns of Roman origin and Iron Age hillforts.

Phase 2

The creation of new towns; both promontory towns -where the existing topography provided part of the defence system, and new towns on open sites – where the defences had to be constructed totally ad novum. These towns were often situated at key points, such as river crossings.

Phase 3

“Filling in the gaps” by the creation of new forts, to ensure that no one in Wessex was more that a day’s march from a burh. Probably the burh of Southwark was also added at this time.