Prehistoric field system and Romano-British cist in Green Bay, Bryher


Heritage Category:
Scheduled Monument
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Date first listed:


Ordnance survey map of Prehistoric field system and Romano-British cist in Green Bay, Bryher
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The building or site itself may lie within the boundary of more than one authority.

Isles of Scilly (Unitary Authority)
National Grid Reference:
SV 87946 14623

Reasons for Designation

The Isles of Scilly, the westernmost of the granite masses of south west England, contain a remarkable abundance and variety of archaeological remains from over 4000 years of human activity. The remote physical setting of the islands, over 40km beyond the mainland in the approaches to the English Channel, has lent a distinctive character to those remains, producing many unusual features important for our broader understanding of the social development of early communities. Throughout the human occupation there has been a gradual submergence of the islands' land area, providing a stimulus to change in the environment and its exploitation. This process has produced evidence for responses to such change against an independent time-scale, promoting integrated studies of archaeological, environmental and linguistic aspects of the islands' settlement. The islands' archaeological remains demonstrate clearly the gradually expanding size and range of contacts of their communities. By the post- medieval period (from AD 1540), the islands occupied a nationally strategic location, resulting in an important concentration of defensive works reflecting the development of fortification methods and technology from the mid 16th to the 20th centuries. An important and unusual range of post- medieval monuments also reflects the islands' position as a formidable hazard for the nation's shipping in the western approaches. The exceptional preservation of the archaeological remains on the islands has long been recognised, producing an unusually full and detailed body of documentation, including several recent surveys. Regular field systems are one of several methods of field layout known to have been employed in the Isles of Scilly from the Bronze Age to the Roman period (c.2000 BC - AD 400); closer dating within that period may be provided by the visible relationships of the field boundaries to other classes of monument with a shorter known time-span of use, or by their relationship with an earlier recorded sea level. They comprise a collection of field plots defined by boundaries laid out in a consistent manner, along two dominant axes at approximate right angles to each other. This results in rectilinear fields which may vary in their size and length:width ratio both within and between individual field systems. The fields are bounded by rubble walls or banks, often incorporating edge- or end- set slabs called orthostats. Within its total area, a regular field system may be subdivided into blocks differing in the orientations of their dominant axes. Regular field systems may be associated with broadly contemporary settlement sites such as stone hut circles. Some regular field systems on the Isles of Scilly contain a distinctive association, rarely encountered elsewhere, whereby certain of their field boundaries directly incorporate or link cairns, entrance graves and cists in some groups of prehistoric funerary monuments. Although no precise figure is available, regular field systems form one of the three principal forms of prehistoric field system, along with irregular field systems and some groups of prehistoric linear boundaries, which survive in over 70 areas of the Isles of Scilly. They provide significant insights into the physical and social organisation of past landscapes and they provide evidence for the wider contemporary context within which other nationally important monuments were constructed.

The field system in Green Bay survives well, clearly displaying the character of the prehistoric land division and its manner of execution. Its extensive survival well into the inter-tidal zone, despite rising sea levels, confirms its long term stability against a considerable period of submergence. It complements the prehistoric field system and settlement survivals at various levels around southern Bryher to provide an unusually complete view of prehistoric land allotment across the altitude range into the now-submerged zone. Consequently this field system is important for the study of prehistoric land-use responses to island environments, given chronological depth in this monument by the evidence for later modification of the walling pattern and by the presence of the Romano-British funerary cist. The proximity of the field system to the cairn cemetery on Samson Hill also demonstrates the relationship between farming, funerary and ritual activities among the prehistoric communities that used this monument. Although subject to some disturbance of its upper levels by wave action, the Romano-British cist provides a rare illustration of land use in this now submerged zone during that later period; its excavation has confirmed its construction and type, while leaving its structure in place. The resulting close dating of this cist has made a valuable contribution to studies of the rate of submergence of the islands' land mass.


The monument includes a prehistoric field system in the inter-tidal zone of Green Bay on the east coast of Bryher in the Isles of Scilly. Slightly beyond the southern end of the field system's known extent is a Romano-British funerary cist. The field system is defined by rubble walls generally 0.5m wide, most being partly masked by surrounding sand and pebble overburden on the middle shore. The walls incorporate almost continuous rows of edge- and end-set slabs averaging 0.3m high but including occasional large boulders. One prominent wall in the north west of the field system differs in containing much larger end-set slabs, to 0.8m high and spaced 0.5m-1m apart. The field system's walls define a pattern of small rectilinear plots, 10m-20m across, bounded by straight or slightly sinuous walls; the axis of their side walls changes from being predominantly north west - south east in the northern sector to WSW-ENE near the centre of the scheduling and returning to almost east-west at the south. Passing through the northern plots are two more sinuous parallel walls, generally 7m apart, running NNE-SSW with traces of a third wall on the same axis 7m east of their visible northern end. These walls are considered to derive from a later prehistoric modification of the field system, resulting in the removal of slabs for their fabric from nearby lengths of the rectilinear plot walls. Towards the centre of the scheduling the longest visible length of the parallel walls curves towards the south. Increasing sand and shingle overburden mantles the southern half of the scheduling masking finer detail from view in that sector; however, 15m south from the east end of the southernmost visible east-west wall are remains of a box-like funerary structure called a cist whose upper edges are exposed on the middle shore. It is of a Romano-British form known as a Porthcressa-type cist, datable to the first to fourth centuries AD and named after a site on St Mary's, Scilly, where their characteristic features were first fully defined. Its visible remains include a setting of small slabs defining an oblong internal area 1.8m long, north-south, by up to 0.9m wide, infilled to within 0.2m of its side slabs by shore sand. Its defining slabs are generally 0.3m- 0.5m long, projecting to 0.2m from the surrounding sand. They include a row of three slabs along the west side, a cluster of at least three slabs across the rounded north end, much encrusted by seaweed, and two slabs across the south end. At least two more slabs survive on the east side but leave a gap to the southern end. These visible remains have clearly been subject to some surface disturbance by wave action and all lower slabs are masked by shore sand. The fuller sub-surface details of the cist were revealed by excavation in the 1970s, confirming the identification as a Porthcressa-type cist. The excavation showed that the cist is ovoid, 1.37m long by 0.76m wide internally. It had been built in a pit dug through the old land surface into the subsoil; its northern end is pointed, defined by edge-set slabs, while the southern end is walled by coursed slab walling. The cist is floored by small laid slabs, unique among known examples of this cist type. Beyond this scheduling, further broadly contemporary field system remains are exposed at a similar inter-tidal level at the northern and southern ends of Green Bay, 200m to the north east and to the south east respectively, with prehistoric settlement sites situated close to the southern remains. These inter-tidal remains on the south east coast of Bryher are complemented on the south west coast by another prehistoric field system and settlement surviving in the inter-tidal zone of Great Porth and extending over the Heathy Hill promontory. On the higher land of Samson Hill, overlooking this scheduling from the south, a prehistoric cairn cemetery is dispersed about the summit area. All of these archaeological features are the subjects of separate schedulings.

MAP EXTRACT The site of the monument is shown on the attached map extract. It includes a 2 metre boundary around the archaeological features, considered to be essential for the monument's support and preservation.


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

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Books and journals
Ratcliffe, J, Lighting up the Past in Scilly, (1991)
Ratcliffe, J, Lighting up the Past in Scilly, (1991)
Thomas, C, Exploration of a Drowned Landscape, (1985)
Ashbee, P, 'Cornish Archaeology' in Ancient Scilly: retrospect, aspect and prospect, , Vol. 25, (1986), 187-219
Ashbee, P, 'Cornish Archaeology' in The Porth Cressa Cist-Graves, St Mary's, Scilly: A Postscript, (1979), 61-80
Ashbee, P, 'Cornish Archaeology' in The Porth Cressa Cist-Graves, St Mary's, Scilly: A Postscript, (1979), 61-80
Ashbee, P, 'Arch Journal' in Excavation of a Cist Grave Cemetery, etc, nr Hughtown, Scilly, , Vol. 111, (1954), 1-25
Parkes, C, AM 107 for Scilly SMR entry PRN 7305, (1988)
Parkes, C, AM 107 for Scilly SMR entry PRN 7306, (1988)
Parkes, C, AM 107 for Scilly SMR entry PRN 7386, (1988)
Parkes, C, AM 107 for Scilly SMR entry PRN 7394, (1988)
Parkes, C/CAU, AM 107 for Scilly SMR entry PRN 7388, (1988)
Ratcliffe, J, Scilly SMR entries PRN 7307.01 & 7682, (1991)
Title: 1:2500 Ordnance Survey Map; SV 8714 Source Date: 1980 Author: Publisher: Surveyor:


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.

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