Swarthy Hill milefortlet 21, 80m south of the Saltpans, part of the Roman frontier defences along the Cumbrian coast


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Scheduled Monument
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Ordnance survey map of Swarthy Hill milefortlet 21, 80m south of the Saltpans, part of the Roman frontier defences along the Cumbrian coast
© Crown Copyright and database right 2020. All rights reserved. Ordnance Survey Licence number 100024900.
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The building or site itself may lie within the boundary of more than one authority.

Allerdale (District Authority)
National Grid Reference:
NY 06732 40029

Reasons for Designation

Hadrian's Wall marks one of the frontiers of the Roman Empire. The international importance of the surviving remains has been recognised through designation as a World Heritage Site. The military importance of the Tyne-Solway route across the Pennines was recognised by the Romans in the second half of the first century AD when a military road, the Stanegate, was constructed along with a series of forts. There is evidence that the Tyne-Solway route was being recognised as a frontier by the start of the second century AD, but the line was consolidated in the early second century AD by the construction of a substantial frontier work, Hadrian's Wall, in c.120 AD. Subsequent attempts to establish the boundary further north, between Clyde and Forth, failed by c.160 AD. Hadrian's Wall then remained the frontier of the Roman Empire in Britain until c.400 AD when Roman armies withdrew from Britain. For most of its course, the 70 miles of Hadrian's Wall running from coast to coast comprised a continuous stone wall (which in places was first temporarily built of turf) with permanent structures sited at intervals of one Roman mile (milecastles) and at third of a mile intervals (turrets) between the milecastles. At a later date, the Wall was strengthened by 16 full-size garrison forts built either on, or close to, the Wall. To the north of the Wall, for most of its length, lay a substantial defensive ditch and to the south a complex of banks and ditches provided east-west communication and demarcated the frontier zone from the province. To the west of Bowness-on-Solway, where the Wall reached the sea, however, the frontier had a different character and served a slightly different purpose. At the western end of the Wall a system of milefortlets and towers, spaced similarly to the milecastles and turrets along the Wall, extended the frontier system for at least 27 miles down the Cumbrian coast and helped control movement across the estuary of the Solway Firth. In places these milefortlets and towers were supplemented by lengths of palisade fences. Throughout its long history the Wall was not always well maintained. It was often neglected and sometimes overrun, but it remained in use until the late fourth century when a weak and divided Roman Empire finally withdrew its armies from the Wall and Britain. The frontier works along the Cumbrian coast survive as earthworks or buried archaeological remains, the latter sometimes visible on aerial photographs. They survive in this form largely as a result of the more ephemeral materials of which they were built (timber and turf instead of the stone of Hadrian's Wall land frontier) rather than because of poor survival of archaeological remains. Components of the coastal frontier which have surviving archaeological remains, whether visible or not, will generally be considered of national importance.

Despite excavation of the milefortlet's interior and consolidation for public display, buried remains of Swarthy Hill milefortlet's defences still survive reasonably well. The monument will contribute to further study of the Roman frontier defences along the Cumbrian coast.


The monument includes the buried and reconstructed remains of Swarthy Hill milefortlet. Within the sequence of milefortlets and towers along the Cumbrian coast this one has been identified as number 21. The milefortlet was originally of turf and timber construction and is located on the cliff top a short distance south of the summit of Swarthy Hill. It was originally discovered in 1968 when aerial photographs revealed the crop marks of the milefortlet's ditch on all sides except the west where the adjacent cliff edge provided sufficient defence. Limited excavations by Turnbull in 1990/1 found the milefortlet to possess east and west entrances, the latter having remains of the posts which suported a 3m square timber tower. An axial road linking the entrances subdivided the fortlet's interior; to the south of this road were found traces of three 5m square earth-walled buildings with an oven and a hearth in two of the structures. To the north of the axial road a line of five stone-packed post holes were found to represent the centreline of a single structure running parallel to the road for virtually the full width of the fortlet. This structure had four doors, each of which led to a separate cubicle or room with a hearth or oven in each. The milefortlet's rampart was constructed of sand revetted with turves and was separated from the ditch by a flat berm up to 5m wide. Finds from the excavation included pottery dated entirely to the Hadrianic period (AD 117-138), fragments of sandstone gaming boards, and ironwork including nails, hobnails, a mattock, two decorative studs and the lid of a small lead box with iron clasps. All fence posts are excluded from the scheduling, although the ground beneath these features is included.

MAP EXTRACT The site of the monument is shown on the attached map extract.


The contents of this record have been generated from a legacy data system.

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Books and journals
Bellhouse, R L, 'Trans Cumb and West Antiq and Arch Soc. New Ser.' in Roman Sites On The Cumberland Coast, , Vol. LXIII, (1963), 142-3
Turnbull, P, 'Archaeology North' in Excavations At Milefortlet 21 In 1990 Interim Summary, , Vol. 1, (1991), 21-7
AP No.s CCC 1595, 28 & 29, Cumbria County Council, Swarthy Hill milefortlet 21,
AP No.s CCC 3059, 23 & 22, Cumbria County Council, Swarthy Hill milefortlet 21,
RCHME, Cumberland Coast Events Record, (1995)
Turnbull,P., Excavations at Milefortlet 21 in 1990 Second Interim Summary, 1992, In Cumbria SMR No. 837


This monument is scheduled under the Ancient Monuments and Archaeological Areas Act 1979 as amended as it appears to the Secretary of State to be of national importance. This entry is a copy, the original is held by the Department for Digital, Culture, Media and Sport.

End of official listing

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