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

List Entry Summary

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.

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

List entry Number: 1016517


The monument may lie within the boundary of more than one authority.


District: Isles of Scilly

District Type: Unitary Authority

Parish: St. Mary's

National Park: Not applicable to this List entry.

Grade: Not applicable to this List entry.

Date first scheduled: 02-Jul-1999

Date of most recent amendment: Not applicable to this List entry.

Legacy System Information

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

Legacy System: RSM

UID: 15534

Asset Groupings

This list entry does not comprise part of an Asset Grouping. Asset Groupings are not part of the official record but are added later for information.

List entry Description

Summary of Monument

Legacy Record - This information may be included in the List Entry Details.

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.

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.


Legacy Record - This information may be included in the List Entry Details.


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 pillbox. 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.

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.

Selected Sources

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

National Grid Reference: SV9083211179


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This copy shows the entry on 23-Sep-2018 at 11:01:16.

End of official listing