Prehistoric linear boundary south east of Horse Rock on Porth Hellick Down, St Mary's

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. The early linear boundaries on the Isles of Scilly were constructed from the Bronze Age to the early medieval period (c.2000 BC-AD 1066): closer dating within that period may be provided by their visible relationships to other classes of monument, or by their relationship with an earlier recorded sea level. They consist of stone walls, up to 3m wide and 1.1m high but usually much slighter, and are formed of heaped rubble, often incorporating edge- or end-set slabs called orthostats. Linear boundaries served a variety of functions. These included separating land regularly cultivated from that less intensively used, separating land held by different social groups, or delineating areas set aside for ceremonial, religious and funerary activities. Linear boundaries are often associated with other forms of contemporary field system. The Isles of Scilly contain examples of an associaton, rarely encountered elswhere, whereby certain linear boundaries directly link several cairns, entrance graves and cists in some groups of prehistoric funerary monuments. Linear boundaries along the coastal margin of the islands are often indistinguishable from the truncated upper walls of early field systems whose remaining extent has been destroyed by the rising sea level. Linear boundaries form a substantial part of the evidence of early field systems recorded on the Isles of Scilly. They provide significant insights into the physical and social organisation of past landscapes and form an important element in the existing landscape. Even where truncated by the rising sea level, their surviving lengths provide important evidence for the wider contemporary context within which other nationally important monuments at higher altitudes were constructed. A substantial proportion of surviving examples are considered worthy of protection.

This linear boundary on Porth Hellick Down has survived well. Its alignment on Horse Rock and its confinement to the coastal slope shows clearly the influence of natural features on the organisation of the landscape during the prehistoric period. Its proximity to other surviving prehistoric field systems and funerary monuments on Porth Hellick Down demonstrates the manner of that organisation and the relationship between farming and religious activities amongst prehistoric communities.

Details

The monument includes a prehistoric linear boundary crossing the eastern slope of Porth Hellick Down on the south east coast of St Mary's in the Isles of Scilly. The linear boundary survives as an almost straight line of small upright slabs and boulders, up to 0.5m high and 1.5m to 6m apart, which extends south east - north west for 17m from the eastern edge of the Down, and is then continued for a further 23m on the same course by traces of a rubble bank, up to 1m wide, 0.1m high and largely blanketed by the heather turf. The boundary is aligned to the north west on a prominent natural granite outcrop called Horse Rock and ends as a visible feature 10m before reaching that outcrop. The monument is located near a number of other broadly contemporary features on Porth Hellick Down: a prehistoric field system extends across the northern and north western parts of the Down, from 55m west of this monument, while across the centre of the Down is a large and diverse group of prehistoric funerary cairns, including the largest surviving cemetery of entrance graves, from 112m south-west of this monument.

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.

Legacy

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

Legacy System number:

15412

Legacy System:

RSM

Sources

Other
Title: 1:2500 Ordnance Survey Map, SV 8715 Source Date: 1980 Author: Publisher: Surveyor:
consulted 1994, CAU, AM 107 for Scilly SMR entry PRN 7527, (1988)
consulted 1994, CAU, AM 107 for Scilly SMR entry PRN 7528, (1988)

End of official list entry

All text content is available under the Open Government Licence v3.0 , except where otherwise stated. Any supplied maps are © Crown Copyright [and database rights] 2026 OS AC0000815036 and may not be reproduced without permission.