Complex sentence: The town did not have a wall, but a protective earthen and wooden palisaded ditch, the outline of which remained visible in the pattern of streets until the mid- 1960s, although the medieval boundary can still be traced now.
Split into simpler sentences: The town did not have a wall, but a protective earthen and wooden palisaded ditch. The outline of this remained visible in the pattern of streets until the mid- 1960s, and the medieval boundary can still be traced now.