From summer 1976 to Autumn 1977 the Canterbury Archaeological Trust excavated within the Rosemary Lane Car Park in advance of redevelopment of the site. The sitecode was RLCP76/77. The site included the north west quarter of the outer bailey of Canterbury Castle. The purpose of the work was to excavate as much of the enclosure as possible, together with the earlier and Medieval levels.
Three areas were looked at, area I in the outer bailey, area II to the north of this and outside the castle enclosure and area III to the east within the bailey. An additional small trench was also cut prior to the constrcution of a new building to the south of Gas Lane, in the Autumn of 1975.
The construction of the gasworks in the 1820s, together with the later extensions, some built as recently as 1953, extensively damaged and polluted the archaeological levels. Only in area II was intact stratigraphy found, elsewhere only deeply cut features survived. These archaeological features became sumps for tar and other noxious by-products of the manufacture of coal gas, which had soaked into the ground. The excavation of Area III was eventually abandoned due to this pollution.
The earliest occupation of the site dated to the mid first century, the evidence for this being a two phase ditch, of possible military design and aligned north east/suoth west. 32.6m out of its 55m uncovered length was excavated and much early Roman pottery was found. A number of human bones were also found, these included a complete male skeleton with a sword cut on the skull. There were two distinct phases of occupation with a final abandonment in c. 70 AD. In area II, Roman street metallings, aligned north east/south west lay over what may have been the demolished rampart of this defensive sequence.
To the east of the street in area II two cremation burials were uncovered, these dated to the late first or early second century. It is thought they were interred in open ground at a time when the area to the west of the street may have been under the plough. Also found to the east of the street were elements of timber structures, constructed around the mid second century or later. A double inhumation, of the second or early third century was found, possibly originating from beneath the structure's floors. These were accompanied by two swords . The building was abandoned in the third or fourth century. Foundations for a more substantial building were located in the small trench south of Gas Lane.
In the post Roman period the early to mid Saxon period sees the deposition of a uniform soil, possibly a plough soil, but no pottery. Sherds of 11th-13th century pottery were found in area II and anumber of late Saxon pits, including two wicker lined wells were investigated. These may be part of pre-castle occupation on the site.
No trace of Norman occupation was found apart from the castle ditch; this was 2.8m deep and 8.9m wide. The clearance of the area prior to the construction of the castle is suggested by a very mixed layer found in the small 1975 trench south of Gas Lane. This was sealed by a layer of plough soil, indicating that the area outside the castle was probably used for agricultural purposes for a considerable period after the castle was built. No trace of the bailey wall was discernable within the excavted area, and were probably removed during the construction of the gasworks. The junction between the bailey wall and the Roman city wall can also still be recognised by a change in wall construction, where the coursed mortared whole flints a the back of the Roman are interrupted by the closely set nineteenth-century knapped flints of the repair following the demolition of the bailey wall.

Bennett, P., Frere, S., Stowe, S., 1982, Excavations at Canterbury Castle (Monograph). SKE29766.