Details

The monument includes a mid-16th century blockhouse built on a low headland at
the south east edge of Old Grimsby Harbour, on the east coast of Tresco in the
Isles of Scilly. The blockhouse was defended from landward attack by a single
close rampart around the western and southern crest of the headland's summit.
Two outer lines of defensive rampart occur on the lower slopes, bringing much
of the headland into the defended area. Coastal erosion along the headland
east of the blockhouse has revealed mortared walling and occupation deposits
within deep deposits of blown sand. The blockhouse is a Listed Building Grade
II and, together with the inner rampart, is a monument in the care of the
Secretary of State.
The blockhouse was built between 1548 and 1552 and survives as a raised gun
platform with adjoining living quarters built of randomly coursed granite
walling with more regular quoins. The walls rise from the weathered, irregular
granite stacks of the underlying outcrops crowning the hill. From there, the
blockhouse commands a field of fire to the north west across the entrance of
Old Grimsby Harbour and to the north east across the waters between Tresco and
Tean, one of several routes of entry to the Scilly archipelago.
The gun platform has four unequal sides, tapering from 7.5m long internally on
the north west to 5.75m long on the south east, and 6.7m long on the south
west to 5.2m long on the north east. The platform level is 2.1m high on the
south west, but ends on the north east against a precipitous drop along the
outcrop's scarp. The platform has a neatly-paved hard-standing, 2m wide, for
artillery along its north west and north east sides. Remains of more irregular
granite paving also survive near the south east wall.
The platform is defined by a parapet, 1m thick, now partly demolished to 0.5m
high or less over the north west, north east and adjoining part of the
south east sides. In the wall-section at each end of the reduced parapet, in
the north west and south east walls, facing slabs survive from former
openings, called embrasures, splayed to both sides to enable guns to fire
through the parapet. On the south west, the wall survives to 2.5m high above
the platform, with an entrance towards the western corner. The entrance, 1.4m
wide and 1.8m high, has a very shallow arch formed from a single lintel slab
and is reached by a step down from the platform; outside the entrance, seven
steps descend to ground level. A small chamber, 0.9m wide and 0.6m high and
now blocked, is located in the inner face of the platform's south west wall
immediately south east of the entrance. High up in the same wall, near the
southern corner, is a blocked narrow window which lit the blockhouse's
original living quarters in this corner; these quarters had a lean-to roof
sloping down to the north east, its former line visible in the outer masonry
of the south east wall.
In the surviving full-height portion of the platform's south east wall, a
small storage chamber is built against and partly into the inner face, near
the southern corner. This chamber, considered to have housed ammunition or
gunpowder, is 1m wide, 0.75m deep and 1.6m high internally, with single-slab
jambs and threshold, rebated for a door, and a projecting bevelled lintel.
Above the chamber and the adjoining portion of this wall, the masonry is
capped by a double layer of bevelled coping slabs.
Between the storage chamber and the platform's southern corner, a slab-framed
doorway, also rebated for a wooden door, opens onto a stairwell that turns
south west, lit by a window in its south east wall, and descends to the later
living quarters. These include a single room built against the blockhouse's
original south west wall, with a lean-to roof sloping down to the south west.
The room measures 3.5m north west - south east by 2.6m north east - south west
internally and is lit by a small window in each of the south west and north
west walls, plus that in the stairwell. A slab-built fireplace is provided in
the south west wall against the southern corner, with a chimney rising from
that corner. The inner faces of the walls bear abundant traces of their former
plaster.
Beyond the blockhouse, the hill slopes gently except to the north east where
the steep coastal slope is crowned by the outcrops underlying the blockhouse.
The approach to the blockhouse across the gentle slope is defended by a single
semicircular rampart around the crown of the hill, ending at the outcrops to
the north east. The rampart is visible as an earthen bank up to 10m wide,
rising 0.35m high on the inner side and 2m high on the outer. The inner edge
of the bank runs 7m-8m beyond the outer walls of the blockhouse, with a
slightly in-turned entrance, 2m wide, in the south west, directly opposite the
blockhouse's entrance steps.
Two further, slighter, ramparts, each 12m-15m wide and approximately 20m
apart, survive on the hill's lower slopes, visible on the west and south west
but extensively masked by deep layers of blown sand that blanket the southern
and eastern sides of the headland. The innermost rampart, to 0.2m high and
chiefly visible on the western slope, runs along the contour 40m-45m beyond
the blockhouse. The outer rampart, up to 1m high, adopts a north west - south
east course near the foot of the south west slope, running towards the saddle
that defines the base of the headland.
In addition to the surviving remains, our knowledge of this monument is
amplified by surviving historical documentation. This blockhouse formed part
of a series of fortifications built on Tresco and St Mary's in 1548-1554
during the reigns of Edward VI and Mary in response to threats from the
French. An account dated May 1554 described this monument as a blockhouse in
the `fissher town', referring to Old Grimsby, and it was accompanied on Tresco
in this phase of fortification by a second blockhouse and an artillery castle
on the opposite side of the island, 1.6km to the north west, covering the
passage between Tresco and Bryher. These fortifications again receive mention
in State Papers of 1579. In 1651, the initial attack from Parliamentary forces
on the incumbent Royalist garrison on Scilly was made on the adjacent stretch
of Tresco's north eastern coastline; this blockhouse is considered to have
played a part in mounting the heavy gunfire which the attackers are recorded
to have faced before they captured the island. In the following year, the
blockhouse is termed `Dover Fort' in the Parliamentary Survey of the islands.
In 1750, Heath commented that the blockhouse commanded Old Grimsby harbour
`when fitted up', suggesting the structure was serviceable but unarmed. The
blockhouse is also recorded by the 18th century antiquaries Borlase and
Troutbeck in 1756 and 1796 respectively.
Along the north east coast of the headland, from 35m ENE of the blockhouse,
erosion of the deep blown-sand deposits has exposed lengths and sections of
walling and adjacent old land surfaces within the dune face. These exposures
indicate two successive parallel mortared walls, 2m apart, following a north
west - south east course, parallel to the present coastline. Although not
closely dated, their mortared construction and their implied length has been
considered to indicate an origin as lines of seaward defence for the
blockhouse.
The earlier, north eastern, wall is visible in two exposures, 90m apart, and
survives as a stone-faced wall, at least 0.8m wide and 1.3m high, with a core
of smaller rubble, all secured by a mortar derived from the local subsoil,
called `ram'. The base of this wall is c.2m below the top of the present dunes
and cuts through a dark band within the dune that derives from a former land
surface when the dune had a period of stability, forming a turf layer. Beneath
this land surface, two earlier land surfaces are visible as dark bands in the
dune face.
The other, later, wall is visible in a single exposure showing only its core
rubble, 0.6m high, also set in ram mortar. This wall's base is c.1.6m below
the present dune surface and was built on the old land surface that is cut by
the other wall. The top of this wall is sealed by another, later and very dark
old land surface layer.
The old land surfaces both above and below the later wall contain waste from
adjacent occupation, evident from numerous limpet shells together with a
fragment of glazed pottery previously recovered from the layer immediately
beneath that wall, indicating a medieval or later date. A slate fragment has
also been found beside the earlier wall section.
All English Heritage notices, fixtures, fittings and modern floor surfaces,
the wooden seat and the post-and-wire fencing are excluded from the scheduling
but the ground beneath them is included.

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

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'
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.

Blockhouses are small, strongly-built defensive structures, built from the
late 14th to mid 17th centuries and designed to house guns and protect the
gunners and ammunition from attack, often while being located in a forward or
exposed position. Blockhouses vary considerably in form, construction and
ground plan but were typically sited as forward defences to cover anchorages,
harbours, other defences and their approaches. They include a single free-
standing structure, usually built of stone, incorporating a gun platform. The
gun platform may be situated in a tower or a bastion. Accommodation for the
gunners or look-out troops was of limited extent if provided at all. Of the 27
blockhouses with extant remains recorded nationally, three are located on the
Isles of Scilly, each of a different design, built during separate periods and
for differing purposes, demonstrating well the diversity of this class of
defensive monument.

The blockhouse at Block House Point has survived well, with relatively minor
damage from the lowering of the parapet wall. The blockhouse is unusual in
including a succession of earthwork defences that complement the masonry
structure. The deep deposits of blown-sand that cover much of the eastern side
of the headland will preserve broadly contemporary occupation deposits and the
blockhouse's seaward defences, confirmed by the walling and land surfaces
evident in the dune face. As an integral part of the first post-medieval phase
of fortification on Scilly, this monument reflects the rise of national
strategic considerations in planning the islands' defences, as evidenced by a
range of surviving historical sources giving the context in which this
monument was built. The provision of improved living quarters and the mid-18th
century indication that the monument was still considered a serviceable
fortification, show an unusual longevity, well beyond that of the other
defences with which it was erected.

Source: Historic England

Sources

Books and journals
Ashbee, P, Ancient Scilly, (1974)
Ashbee, P, Ancient Scilly, (1974)
Borlase, W, Observations on Ancient and Present State of the Isles of Scilly, (1756)
Bowley, R L, The Fortunate Islands: A History of the Isles of Scilly, (1968)
Bowley, R L, The Fortunate Islands: A History of the Isles of Scilly, (1968)
Bowley, R L, The Fortunate Islands: A History of the Isles of Scilly, (1968)
Heath, R, A Natural and Historical Account of the Isles of Scilly, (1750)
Morgan, K O, Oxford Illustrated History of Britain, (1986)
O'Neil, BH St J, Ancient Monuments of the Isles of Scilly, (1949)
O'Neil, BH St J, Ancient Monuments of the Isles of Scilly, (1949)
Ratcliffe, J, Fieldwork in Scilly 1991 and 1992, (1993)
Ratcliffe, J, Fieldwork in Scilly 1991 and 1992, (1993)
Ratcliffe, J, Fieldwork in Scilly 1991 and 1992, (1993)
Ratcliffe, J, Fieldwork in Scilly 1991 and 1992, (1993)
Ratcliffe, J, Scilly's Archaeological Heritage, (1992)
Ratcliffe, J, Scilly's Archaeological Heritage, (1992)
Ratcliffe, J, The Archaeology of Scilly, (1989)
Saunders, A D, 'Cornish Archaeology' in Harry's Walls, St Mary's Scilly; a new interpretation, (1962), 85-91
Saunders, A D, 'Cornish Archaeology' in Harry's Walls, St Mary's Scilly; a new interpretation, (1962), 85-91
Other
Ancient Monuments Terrier & Deed Plan for SI 356, Old Blockhouse, (1984)
Ancient Monuments Terrier & Deed Plan for SI 356, Old Blockhouse, (1984)
consulted 1993, Parkes, C, AM 107 for Scilly SMR entry PRN 7375.01, (1988)
consulted 1993, Parkes, C, AM 107 for Scilly SMR entry PRN 7375.02, (1988)
consulted 1993, Parkes, C/CAU, AM 107 for Scilly SMR entry PRN 7364.01, (1988)
consulted 1993, Parkes, C/CAU, AM 107 for Scilly SMR entry PRN 7364.01-.02, (1988)
consulted 1993, Parkes, C/CAU, AM 107 for Scilly SMR entry PRN 7364.02, (1988)
consulted 1993, Parkes, C/CAU, AM 107 for Scilly SMR entry PRN 7365.02, (1988)
consulted 1993, Parkes, C/CAU, AM 107 for Scilly SMR entry PRN 7375.01, (1988)
consulted 1993, Parkes, C/CAU, AM 107 for Scilly SMR entry PRN 7375.02, (1988)
consulted 1993, Parkes, C/CAU, AM 107s for Scilly SMR entries PRN 7364.01 & 7365.02, (1988)
consulted 1993, Parkes, C/CAU, AM 107s for Scilly SMR entries PRN 7364.01-2; 7365.02; 7375.01-2, (1988)
p 73; Tresco The Blockhouse 0/1/119, DNH, DNH List of Buildings of Special Architectural/Historic Interest, (1992)
Title: 1:10000 Ordnance Survey Maps: SV 81 NE & SV 91 NW
Source Date: 1980
Author:
Publisher:
Surveyor:

Title: 1:2500 Ordnance Survey Map, SV 8715
Source Date: 1980
Author:
Publisher:
Surveyor:

Source: Historic England