Prehistoric field system and post-medieval quay in Great Porth, Bryher


Heritage Category:
Scheduled Monument
List Entry Number:
Date first listed:


Ordnance survey map of Prehistoric field system and post-medieval quay in Great Porth, Bryher
© Crown Copyright and database right 2019. All rights reserved. Ordnance Survey Licence number 100024900.
© British Crown and SeaZone Solutions Limited 2019. All rights reserved. Licence number 102006.006.
Use of this data is subject to Terms and Conditions.

The above map is for quick reference purposes only and may not be to scale. For a copy of the full scale map, please see the attached PDF - 1014987.pdf

The PDF will be generated from our live systems and may take a few minutes to download depending on how busy our servers are. We apologise for this delay.

This copy shows the entry on 13-Nov-2019 at 01:41:49.


The building or site itself may lie within the boundary of more than one authority.

Isles of Scilly (Unitary Authority)
National Grid Reference:
SV 87516 14406

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 Great Porth survives reasonably well, clearly displaying the character of the prehistoric land division. Its extensive survival well into the inter-tidal zone confirms its long term stability against a considerable period of submergence. This sector of the field system complements that at higher levels which survives with the prehistoric settlement on Heathy Hill, providing an unusually complete view of prehistoric land allotment across the altitude range into now-submerged levels. This field system is one of very few inter-tidal survivals on Scilly situated on a shore facing out from the core of the archipelago. As a result of these factors this monument is of particular importance for Scilly's contribution to the study of land-use responses to island environments during the prehistoric period. The wider contemporary context of this monument and its relationship to prehistoric funerary and ritual activity is demonstrated by the field systems and cairn cemeteries on Samson Hill and Gweal Hill. The association of the abandoned post-medieval quay in this monument with the kelp pit on Heathy Hill illustrates the main visible surviving elements of kelp-burning, a formerly major economic activity in the islands' economy.


The monument includes a prehistoric field system surviving on the shore of the southern half of Great Porth, a rounded bay on the west coast of Bryher in the Isles of Scilly. The field system incorporates an abandoned post-medieval quay near the southern end of the bay. The north west periphery of this monument includes an area below Mean Low Water level. The field system is defined by walls of heaped rubble and continuous rows of larger slabs, generally 0.5m to 1m wide and 0.4m high. The walls incorporate occasional edge-set slabs, called orthostats, commonly 0.5m high; in the field system's longest wall the orthostats are larger, up to 0.8m high, and are spaced at intervals along the wall, 2m-5m apart. The field system contains at least four walls subdividing the gently shelving shore on ESE-WNW alignments, 18m to 70m apart. Their known eastern and western extents differ with local variations in thickness of the pebble and sand overburden on the shore in the centre and north of the scheduling and of rubble on the boulder shore in the south. However near the centre of the scheduling, the longest of these walls extends WNW below the present Mean Low Water level before curving to adopt a south westerly course, rising up the present middle shore of the Heathy Hill promontory and intersecting another of the ESE-WNW walls shortly before its limit of visibility on the boulder shore. On the upper shore in the south east of the scheduling, limited scouring of the sand cover has revealed two areas of finer subdivision within the larger scale strips; one includes at least two lengths of walling 7.5m apart on a NNE-SSW axis, at right angles to the dominant strip axis; the other includes a curved stagger in a short exposure of ESE-WNW wall. This field system forms the north eastern continuation of a prehistoric field system that also survives, with a hut circle settlement, over most of the adjacent Heathy Hill promontory from 17m to the south west of this scheduling. This is the subject of a separate scheduling. The nearest prehistoric boundaries on the promontory share the dominant ESE-WNW alignments found in this monument, crossed by north east - south west walls running down the slope. These two areas of the field system's survival reflect relatively low rates of erosion on the promontory and, despite submergence by rising sea levels, on the very gently sloping surface of the bay. They are separated by a zone of active erosion and archaeological destruction where the rising sea level has reached the steeper gradient along the edge of the promontory. In addition to the visible remains of the field system, a number of prehistoric flint artefacts have been recovered from various locations adjacent to the field boundaries. In the south of the area of the scheduling, a long-abandoned post-medieval quay extends 19m north from a point slightly below Mean High Water level at the southern end of the bay's curve. The quay survives as a broad boulder wall, 1.75m wide and 0.6m high, built over exposed bedrock on the shore. The quay is faced along its eastern side by a closely-spaced line of slabs, backed by a less organised scatter of boulders which has been partly disrupted by wave action. This quay has been identified as a `small pier' mentioned in 1794 by the local churchman and antiquary John Troutbeck. It is also considered that the quay will have served as an off-loading point for seaweed to serve a kelp pit on the northern edge of Heathy Hill, 130m to the west, where seaweed was burnt to produce soda ash in a local industry practised between AD 1684 and 1835 supplying a vital commodity for the mainland glass, soap and alum industries. Beyond this scheduling and the prehistoric field system's adjacent extension onto Heathy Hill, further broadly contemporary field system remains survive on the higher lands of Samson Hill and Gweal Hill, from 275m to the south east and 450m to the north west respectively, giving way to cairn cemeteries about their summit areas. These archaeological features are the subject 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.

Legacy System number:
Legacy System:


Books and journals
Ratcliffe, J, Lighting up the Past in Scilly, (1991)
Tangye, M, 'CAS Newsletter; October 1980' in News from the Area Correspondents, , Vol. 34, (1980), 4-5
Parkes, C/CAU, AM 107 for Scilly SMR entry PRN 7389, (1988)
Parkes, C/CAU, AM 107 for Scilly SMR entry PRN 7390, (1988)
Parkes, C/CAU, AM 107 for Scilly SMR entry PRN 7393, (1988)
Parkes, C/CAU, AM 107s for Scilly SMR entries PRN 7384 & 7394, (1988)
Parkes, C/CAU, AM 107s for Scilly SMR entries PRN 7385 & 7395, (1988)
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.

End of official listing

Your Contributions

Do you know more about this entry?

The following information has been contributed by users volunteering for our Enriching The List project. For small corrections to the List Entry please see our Minor Amendments procedure.

The information and images below are the opinion of the contributor, are not part of the official entry and do not represent the official position of Historic England. We have not checked that the contributions below are factually accurate. Please see our terms and conditions. If you wish to report an issue with a contribution or have a question please email [email protected].