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Prehistoric chambered cairn 60m north of Knackyboy Carn, St Martin's

A Scheduled Monument in St. Martin's, Isles of Scilly

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Latitude: 49.9635 / 49°57'48"N

Longitude: -6.2913 / 6°17'28"W

OS Eastings: 92360.66039

OS Northings: 15863.029035

OS Grid: SV923158

Mapcode National: GBR BXVS.93J

Mapcode Global: VGYBY.W5XT

Entry Name: Prehistoric chambered cairn 60m north of Knackyboy Carn, St Martin's

Scheduled Date: 24 October 1972

Last Amended: 29 April 1998

Source: Historic England

Source ID: 1018112

English Heritage Legacy ID: 15520

County: Isles of Scilly

Civil Parish: St. Martin's

Traditional County: Cornwall

Lieutenancy Area (Ceremonial County): Cornwall

Church of England Parish: Isles of Scilly

Church of England Diocese: Truro


The monument includes a large prehistoric chambered cairn, of a type known as
an entrance grave, overlooking the steep southern slope of western St Martin's
in the Isles of Scilly.
The cairn survives on the crest of the southern slope as a large ovoid mound,
19m north west-south east by 16m north east-south west, rising to 0.9m to a
flattened upper platform. A slightly raised central area on the platform
surface is defined by a low bedrock outcrop and at least three slabs from an
inner kerb, roughly 7.5m in diameter and 0.4m high, within which is a shallow
rectangular depression, 3m long east-west, denoting the cairn's funerary
Although now largely covered by dense vegetation, excavation during 1948 in
and immediately around the chamber has considerably increased our knowledge of
this cairn's internal structure and the prehistoric funerary activity
associated with it.
The excavation revealed that the mound is built around a large bedrock outcrop
which rises towards the centre of the platform. The cairn's funerary chamber
is rectangular, measuring 3.7m long east-west by 1m wide internally and
defined across the west end and the western part of its north side by faces of
the bedrock outcrop. Beyond this, the north and south sides are walled by
rubble set in a mortar made from the local granite subsoil and which extended
over parts of the chamber's inner wall face; a portion of the north wall was
disrupted by earlier antiquarian digging. The chamber entrance is on the east,
constricted to 0.75m wide by flanking edge-set slabs.
The chamber contained abundant and rich funerary deposits reflecting a complex
sequence of ritual activity. The lower western end was levelled up and partly
paved with flat slabs. Nearby, a hollow filled with charcoal and sand was
overlain by a flat slab supporting a near-complete funerary urn; behind that
two rows of three urns extended across the west of the chamber. Another urn
stood at the centre of the chamber. All of these urns contained cremated bone
fragments; the chamber's central urn also contained a glass bead and in the
soil near that urn's base was a small star-shaped bead made of a greenish
artificial material called faience, similar to a small number of such beads
known from funerary monuments dating to the 2nd millennium BC mainly in
southern England and Scotland.
Spread around and partly over these urns was a thick deposit of charcoal,
cremated bone and some soil, extending along and filling much of the chamber
interior. Included within this deposit were large fragments of more urns, two
small bronze artefacts and four rounded glass beads.
The final deposition within the chamber comprised a further eight urns,
complete or nearly so, placed onto that thick layer of charcoal, bone and
artefacts: three were arranged along the midline at the centre and east of the
chamber, with the others to each side.
The excavation also found a separate focus of funerary activity beyond the
chamber, 1m south of its western end, where two more urns were found within a
small stone setting. Nearby and beneath the base of the cairn's rubble was a
flint adze considered to be of neolithic date, earlier than the cairn and
deriving from the old soil layer on which the cairn was later built.
The cremated bone recovered from the excavation has been suggested as
representing 60 - 70 individuals, accompanied by a very considerable amount of
prehistoric pottery, over 200kg in total, much of which was decorated using
incised lines or the impressions of comb-teeth or threads, and many urns bore
handles formed as lugs, some of which are perforated. A further four small
glass beads were also found during the excavation, not directly associated
with recorded layers though closely comparable in form with those from the
cairn's chamber.

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.

Source: Historic England

Reasons for Scheduling

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'
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.
Entrance graves are funerary and ritual monuments whose construction and use
dates to the later Neolithic, Early and Middle Bronze Age (c.2500-1000 BC).
They were constructed with a roughly circular mound of heaped rubble and
earth, up to 25m in diameter, whose perimeter may be defined by a kerb of
edge-set slabs or, occasionally, coursed stone. The mound contains a
rectangular chamber built of edge-set slabs or coursed rubble walling, or a
combination of both. The chamber was roofed by further slabs, called
capstones, set across the chamber. The chamber was accessible via a gap in the
mound's kerb or outer edge and often extends back beyond the centre of the
mound. The cairn's mound and chamber may incorporate natural boulders and
outcrops. Excavations in entrance graves have revealed cremated human bone and
funerary urns, usually within the chambers but on occasion within the mound.
Unburnt human bone has also been recovered but is only rarely preserved. Some
chambers have also produced ritual deposits of domestic midden debris,
including dark earth typical of the surface soil found within settlements,
animal bone and artefact fragments. Entrance graves may occur as single
monuments or in small or large groups, often being associated with other cairn
types in cemeteries. They may also occur in close proximity to broadly
contemporary field boundaries. The national distribution of entrance graves is
heavily weighted towards the Isles of Scilly which contain 79 of the 93
surviving examples recorded nationally, the remaining 14 being located in
western Cornwall.

The chambered cairn near Knackyboy Carn is one of the largest prehistoric
cairns on Scilly and survives reasonably well, the excavation and earlier
antiquarian activity being limited to the chamber and a section of the mound
to each side. Most of the mound is unexcavated along with such funerary
deposits and structures as have been confirmed beyond the south of the chamber
and, sealed beneath the cairn, the early soil on which the cairn was built and
which contained one of the rare neolithic artefacts to be recovered from
Scilly. This is one of very few chambered cairns where undisturbed internal
features have been recorded in sufficient detail to give a good understanding
of the funerary and ritual activity that it embodied, the resulting
information making a valuable contribution to our knowledge of these aspects
and adding further to the importance of the unexcavated parts of this cairn.
The huge pottery assemblage from the cairn contains a diversity of forms and
decoration which provide an important source of reference for future studies
of prehistoric pottery from south west England. The faience and glass beads
from the chamber deposits are unique on Scilly and nationally very rare finds
from this period, again marking out this cairn as highly unusual and enhancing
the value of its unexcavated areas.

Source: Historic England


Books and journals
Ashbee, P, Ancient Scilly, (1974)
Ashbee, P, Ancient Scilly, (1974)
Ashbee, P, Ancient Scilly, (1974)
O'Neil, BH St J, Ancient Monuments of the Isles of Scilly, (1949)
Thomas, C, Exploration of a Drowned Landscape, (1985)
Thomas, C, Exploration of a Drowned Landscape, (1985)
O'Neil, B H S, 'Antiquaries Journal' in The Excavation of Knackyboy Cairn, St Martin's, Isles of Scilly, , Vol. XXXII, (1952), 21-34
Butcher, S A, AM 7 & maplet for Scilly County Monument SI 850, (1971)
Thorpe, C/CAU, AM 107 for Scilly SMR entry PRN 7162.01, (1988)
Thorpe, C/CAU, AM 107 for Scilly SMR entry PRN 7162.02, (1988)
Title: 1:2500 Ordnance Survey Map; Cornwall sheet LXXXII: 15
Source Date: 1889
Both 1889 and 1908 editions
Title: 1:2500 Ordnance Survey Map; SV 9215
Source Date: 1980

Source: Historic England

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