Ancient Monuments

History on the Ground

This site is entirely user-supported. See how you can help.

World War II pillbox between Thomas' Porth and Porthaloo, St Mary's

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

We don't have any photos of this monument yet. Why don't you be the first to send us one?

Upload Photo »

Approximate Location Map
Large Map »

If Google Street View is available, the image is from the best available vantage point looking, if possible, towards the location of the monument. Where it is not available, the satellite view is shown instead.


Latitude: 49.9207 / 49°55'14"N

Longitude: -6.3088 / 6°18'31"W

OS Eastings: 90831.982

OS Northings: 11178.553822

OS Grid: SV908111

Mapcode National: GBR BXTW.M31

Mapcode Global: VGYC4.L8N4

Entry Name: World War II pillbox between Thomas' Porth and Porthaloo, St Mary's

Scheduled Date: 2 July 1999

Source: Historic England

Source ID: 1016517

English Heritage Legacy ID: 15534

County: Isles of Scilly

Civil Parish: St. Mary's

Built-Up Area: Hugh town

Traditional County: Cornwall

Lieutenancy Area (Ceremonial County): Cornwall

Church of England Parish: Isles of Scilly

Church of England Diocese: Truro


The monument includes a World War II pillbox near the tip of a small headland
separating the bays of Thomas' Porth and Porthloo on the west coast of St
Mary's in the Isles of Scilly. It is situated immediately behind the upper
shore, built into the hedge-line of a former small field which has since been
opened up to form part of the Porthloo boatyard facilities.
The pillbox has an irregular hexagonal plan with a concrete raft floor which
extends up to 0.2m beyond the outer wall face. The floor supports walls faced
with an outer skin of mortared concrete blocks around a shuttered concrete
core and inner face. A flat shuttered concrete roof is edged by the topmost
course of the walls' outer skin. The pillbox has wall faces roughly 2.1m
across externally but with a broader rear wall, facing ENE, to contain the
doorway. The doorway opens to a short entrance passage accommodated in a small
rectangular block-built extension against the rear wall; the end wall of this
passage extends slightly into the interior where it meets the rear wall of the
The pillbox is about 2m high externally and provided with three rectangular
gun loopholes, one each in the wall faces looking out over Porthloo and
Thomas' Porth, the field of fire over the latter extending across the
anchorage of St Mary's Pool to Hughtown Pier. The loopholes are 0.2m wide and
0.25m high, with surrounds chamfered on the inner face, stepped on the outer
face. The loopholes have a small metal peg to each side on the outer face and
one loophole has an exposed and corroding steel bar forming a lintel over its
outer side. The rear of the pillbox was covered from two smaller loopholes,
one each in the end and side walls of the entrance passage. The pillbox was
partly masked by being sunken slightly below the ground level of the hedge-
line behind the upper shore; the adjacent hedgerow shrubs would further assist
in its masking as they do today, and the roof was camouflaged from aircraft by
an earth and turf capping which still survives largely intact.
Contemporary sources record an anti-invasion system of 27 pillboxes and
defended gun positions around the coast of St Mary's, within which this
pillbox was designated `Pillbox No.14'. It occupied an important location,
with a field of fire covering the approach to the St Mary's Pool anchorage and
to Hughtown, the islands' administrative centre and main population focus; it
also covered the potential landing beaches of Thomas' Porth and Porthloo, both
providing easy access to Hughtown and to an RAF station and radio masts to the
north east at Telegraph. This pillbox was the north eastern of nine originally
sited along the coasts and headlands fringing St Mary's Pool, highlighting the
strategic importance of the bay; of those nine, this is the only example to
survive substantially intact. It was built between January and April 1941
along with the rest of the anti-invasion defences erected around St Mary's.
This particular pillbox appears in operational instructions issued in July
1941, designed to counter any enemy landings on St Mary's, in which it was
specified to be manned by the 1st Platoon of the island's Home Guard, who were
to be armed with Browning guns and automatic rifles.

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.

World War II pillboxes are built and heavily protected defensive gun
positions, mostly for infantry with rifles and machine-guns but larger forms
housed light artillery, notably anti-tank guns and light anti-aircraft guns.
They are generally grouped around vulnerable or strategically important nodal
points, installations and areas, or arranged along linear defensive systems
designed to obstruct the enemy's advance across the country. Pillboxes first
appeared widely as a defensive element in the relatively static trench warfare
of World War I. Gradual development over the following two decades was
superceded in early 1940 by design principles born from the practical
experience of British troops in France, giving a shell-proof reinforced
concrete construction whose hexagonal plan had a gun loophole in each facet
giving all-round cover, strongly influencing designs issued from May 1940 by
the War Office and by the Chief Engineers of the regional Commands.
Nationally, pillbox construction began in late May 1940 as a key part of the
rapid programme of anti-invasion defences initiated after the fall of France
to German troops. By October 1940, over 14,000 shuttered concrete pillboxes
had been built, supplemented by large numbers in other construction techniques
and a small number of commercially-produced pillbox designs. Various forms of
camouflaged facing were employed and others were hidden within existing
structures, depending on local circumstances. By early 1941 however, the
tactical concepts underlying pillboxes, especially their deployment to provide
linear defensive lines, were becoming criticised as being too inflexible,
costly and impracticable as an effective defensive system, with increasing
reliance being placed on dug fieldworks around vulnerable points and the use
of mobile troop units. This shift in policy culminated in February 1942 in an
order requiring no more to be built as they were deemed unsuitable, by which
time over 20,000 pillboxes had been completed.
World War II defences on the Isles of Scilly were largely directed to the
protection of St Mary's, and particularly Hughtown and the Garrison, with only
isolated machine-gun posts on some off-islands. Provision of its anti-invasion
defences came relatively late, with a system of 27 pillboxes and defended gun
positions built around the St Mary's coastline between January and April 1941
by the 14th Battalion Royal Fusiliers under guidance from 231A Fd Coy Royal
Engineers. Most were sited around the Garrison and the bays immediately
adjacent to Hughtown, with single or small groups of pillboxes overlooking
other potential landing beaches. Most adapted standard issued designs, but
some were ingeniously masked within existing structures, especially around the
Garrison. Of the original 27, nine survive virtually intact, with remains of
two others subsided from their former positions. The remainder were
demolished, mostly in 1946, though visible traces survive of at least five of
those. This latest defensive phase on Scilly complements the well preserved
remains from a 400 year sequence of national defensive systems deployed on the
islands, providing a rare and valuable resource for studying developments in
military technology and strategic thinking over that period. Consequently the
nine virtually intact pillboxes still in their original positions are
considered worthy of protection.
The pillbox between Thomas' Porth and Porthloo survives substantially intact;
its position and grouping with the other pillboxes around St Mary's Pool show
clearly the tactical thought which underlay the siting of pillboxes. Its role
within the overall anti-invasion system on Scilly is amply confirmed by its
relationship with the other surviving pillboxes and their remains, and by the
detailed documentary sources which bear on both that system and this
particular pillbox.

Source: Historic England


Osborne's Scill War Diary 39-45 vol 3 Extracts in Osborne as below, Appendix aj, War Diary of 13 Btn West Yorks Regiment, July 1941, (1941)
Osborne's Scill War Diary 39-45 vol 3, Extracts in Osborne as below, Appendix ak, War Diary of 14 Btn Royal Fusiliers, Jan-May 1941, (1941)
Title: 1:10000 Ordnance Survey Map; SV 91 SW
Source Date: 1980

Title: Map of St Mary's pillbox locations and Nos by 14Btn Royal Fusiliers
Source Date: 1941
Osborne's Scill War Diary 39-45 vol 3

Source: Historic England

Other nearby scheduled monuments is an independent online resource and is not associated with any government department. All government data published here is used under licence. Please do not contact for any queries related to any individual ancient or schedued monument, planning permission related to scheduled monuments or the scheduling process itself. is a Good Stuff website.