In 2008 a trial trenching evaluation was carried out at Horsewash Lane in advance of possible development.The report desribes how the wall in trench 3 " was bonded with a large masonry structure at its northern end. This structure measured 1.89m high by 2.80 east west and 2.50m north south. This masonry was circular to polygonal in form and was comprised of three tiers. The core of this structure extended another 0.40m above the top of the third tier to a height of 4.00m OD. The core comprised flint nodules set into a hard pinkish mortar."

The report provided a number of interpretations of this masonry structure as quoted below: "It is unclear what the exact purpose or function of this structure was except that it is clearly related to or part of the Roman city wall. Several very tentative suggestions can be made however. Firstly, it could be a bastion. This would be unusual, although not unique, in that the observed curvature is internal to the city wall, where as bastions from the province more typically have hollow or flush interior elevations. Secondly, it could be internal buttressing to pin and hold a substandard or subsiding part of the city wall. This however seems unlikely given that it was bonded and contemporaneous to what appears to be the original city wall and was constructed on a rubble raft not trench built. Thirdly, it could form part of a gatehouse for a previously unknown access road or point along Horsewash
Lane. This interpretation is supported by a number of aspects of the evidence: the discontinuous earthen bank observed in trenches 2/10 and 5 but not observed in trench 3 is suggestive of an opening or gateway in the wall; it is possible that if the settlement boundaries did indeed move towards
the river, as is suggested, then this gateway could be a result of the retention of a previous extra-mural access way to the river. Conversely there is no evidence for Horsewash Lane having been a Roman street and no mention of a gate in the later Saxon charters. A fourth potential interpretation is that this structure is a Roman lighthouse or Pharos incorporated into the city wall. Certainly it would have been in the right position to be viewed by landward bound shipping coming in to Rochester
harbour. Its polygonal form is also reminiscent of the octagonal Pharos at Dover Castle."

"This structure was underlain by a probable consolidation deposit containing pottery dated to AD 270-350." (4)

<4> Archaeology South-East, 2008, An Archaeological Evaluation at PB Site, Horse Wash Lane, Rochester (Unpublished document). SKE31443.