one should perhaps take note of somewhere like Newark. In the case of that
town a substantial wall and ditch existed from the late Saxon times but by
the mid 14th century was almost completely removed to allow for town
expansion. It was replaced with a much less substantial wall which followed
the original route but was little more than a boundary feature deliniating
the town itself from the newer suburbs for the purposes of tax. Some
sections of later wall remain and are often decried as being too
insubstantial as to be part of the town wall. The error here is that
although they are not part of the 'original' wall which topped a large
bank, they are probably part of the later boundary and therefore do have
historical and archaeological significance.
If you like I can send you copies of the excavation reports on the various
sections of the wall that have been examined during development over the
past 30 years or so.