The following is a summary of the periods into which results of the excavations on Site B (the Saxon defences) are arranged (Figure 3). These periods are put forward as a model which is designed to articulate the archaeological data from all the various trenches and areas in terms of processes (e.g. construction, weathering, destruction) which can be inferred to have taken place, and which explain the observed stratigraphy in a consistent way. It must be understood that the definition of this scheme is dependent on inferences about the processes and agencies which have been involved in the formation of the archaeological deposits. However, the evidence from all parts of the site, as well as that from earlier excavations, provides support for the validity of these divisions. The dating and historical contexts of these periods are discussed fully in Part 3 where some attempt is made to place these periods in the context of known historical events.
Figure 8: Animated reconstruction of the four principal development phases of the defences [see Figure 8a for a static isometric bird's-eye view]
Period 0 - Before the construction of the defences.
Period 1 - Construction of the following elements of the defensive system of the fortress:
A bank of dump construction made of clay and turf, with the front and rear revetments of stacked turf (without a fronting wooden palisade). The turf would have been stripped from the area of the bank, berms and ditches, and the clay derived from the excavation of the ditches;
Three shallow ditches, separated from the bank and each other by berms, the outer one rather wider than the other two;
A walkway or street (intra-mural walkway or wall street) about 1.2m in width laid out around the inner edge of the bank, made of flat stones laid directly on the original turf as probably the primary feature in the defensive system;
A simple wooden turret at the internal corner of the bank, possibly allied with a wooden palisade along the top of the bank.
Probably late 9th century - c. 878-9.
Period 2A - A general strengthening of the defences, which involved:
the replacement of the front turf revetment by a substantial partially mortared stone wall, leaving construction deposits spread over the berm between the wall and the inner ditch;
the cleaning out of the two inner ditches;
the heightening of the bank;
the construction of a small stone wall part way up the tail of the bank (inferred from its destruction deposits at the rear of the bank), possibly to revet a wall walk or platform at the top of the bank.
Probably early 10th century - 904-911.
Period 2B - The elapse of a long period, marked by:
the accumulation of weathering products on the berm;
the partial or nearly complete silting of the ditches, and the partial erosion of their sides;
the deposition of soil and small stones over the intra-mural walkway;
the partial collapse of the rear revetment wall down the back of the bank on to and beyond the intra-mural walkway.
Second to fourth quarter of the 10th century.
Period 2C - A partial refurbishment of the defensive system, which involved the re-excavation of the inner ditches.
Early 11th century.
Period 3A - A dramatic episode which appears to have amounted to the systematic destruction of the defensive capability of the burh, which involved:
the near total destruction of the wall fronting the bank, with the destruction debris being piled onto the inner berm;
the filling of the two inner ditches with stones;
the destruction of the wall built at the rear of the bank, its stones scattered over the area to the back of the bank.
Probably early 11th century - c. 1016.
Period 3B - The erosion and degradation of the remaining bank and debris on the berm over a long period, and the silting of what remained of the ditches.
Early 11th - mid 12th centuries.
Period 4A - The redefence of the town, which involved the construction of the following elements:
a substantial wooden palisade along the line of the former wall;
a wide shallow ditch, on the W side some way out from the palisade, on the S side close to it;
the re-excavation of the inner ditch on the W side;
the excavation of a substantial ditch on the inside of the southern part of the Saxon bank (trench 1 only).
Probably mid 12th century - c. 1144.
This was followed by an appreciable period in which the ditches were then allowed to fill up, and the timber palisade to deteriorate.
Period 4B - at least one episode of refurbishment of the defences, involving the replacement or rebuilding of the front palisade and the partial re-excavation of the ditches.
Period 5 - A long period represented by the abandonment and decay of the defences of period 4B, with further erosion of the bank partly caused by cultivation, and the use of the W bank as a ridge in a ridge and furrow system.