A study of the pillbox at Murlough Beach

For those of you who are familiar with the beach at Murlough Bay nature reserve, you may have noticed a rather unassuming pile of rubble. Without interpretation you may have thought this had been dumped some decades ago, but it provides a convenient sitting place or playground for adventurous children. It is in fact a demolished Second World War pillbox. Built in the tens of thousands across the United Kingdom between 1940 and 1941 to form impenetrable defensive lines around the coast and across the country, they are iconically the most enduring aspect of wartime life that remain today.

I had first visited this box on a walk in around 2008, but only took a handful of photographs. Since then, the Ulster Archaeological Society has previously undertaken a study of the site (Welsh, Cooper, Scott, 2011) and the remains have continued to erode and dissolve into the Irish Sea. I paid them a visit in January 2021 and took a series of photographs in an attempt to interpret what remained, and to challenge some of the assumptions made in the UAS report.

For information on how a pillbox was constructed, you can read my article on the subject based on contemporary documents and data.

Background

The South Down coast was prime invasion territory. Bounded to the south by a neutral country (Eire), and to the east by the Irish Sea, miles and miles of gentle flowing beach and agricultural land, an enemy could mount an invasion by sea. The only disadvantage the south Down coast had over the north Antrim coast was the proximity of England; any invasion would have to navigate the south coast of England the enter Irish Sea before making their way northward, and with a complex network of radar stations and coast watching posts, this would have been difficult to achieve while maintaining the element of surprise. Never the less, the coast was protected. A series of protected pillbox were constructed, and access to the beaches denied by means of anti-landing obstacles to prevent aircraft or flat bottomed boats from gaining a foothold. The pillbox at Murlough Beach was one of these protected pillboxes. The map below shows the locations of surviving pillboxes in South Down, with the demolished example at Murlough Bay being in the centre of the image, by Dundrum Bay.

From Newcastle to the south through to Minerstown at the eastern end of Tyrella Beach, there are eight surviving pillbox locations. For the purposes of interpretation, I have drawn on range rings, each at 550 yards, the effective range of the Bren Light Machine Gun (LMG). For a defensive position to have complete efficiency, it must be able to provide interlocking arcs of fire with its neighbour. For the complete defensive picture, each circle (gun) should be overlapping with two other posts. This is not always possible, for reasons such as terrain, manpower or weapons; so what also complimented these pillboxes were beach defences, and both Murlough and Tyrella both had wooden anti-landing obstacles and beach scaffolding to deter invaders. I am unsure if Northern Irish beaches were mined similar to those beaches at risk in the south of England.
Surviving wooden anti-landing poles at Murlough Beach. These obstacles would have been covered by the machine gun fire from the pillbox (2008 © Author)
A single remnant of beach scaffolding, also known as Obstacle Z.1, on Tyrella Beach, County Down. It is approximately 1m in height, with a rough concrete base. Large expanses of scaffolding would have been used to prevent landing craft from approaching the beach and would have been submerged at the low water mark (2021 © Author)

Site visit (2008)

Irish Grid ReferenceJ 41344 34563
Latitude / Longitude54.240543, -5.8324328

Even with only a handful of images (below, click to enlarge), I have been able to glean more information from the debris than on my single 2021 visit. The rate of coastal erosion in the last 12 years has been quite extreme, and a number of key features to assist in identification have been lost or are close to it.

Site visit (2021)

Returning around twelve years later, the pillbox is almost unrecognisable. The dunes have retreated approximately 25 meters from their previous position, but more of the pillbox is now visible. The prolonged exposure has resulted in a greater amount of erosion to the concrete surface and corners, and the once subtle signs of rust leeching from internal metalwork are now almost impossible to spot.

The exposed ruins of the Murlough Beach pillbox currently do little to fight off the tide never mind an armed invasion (2021 © Author)

With more of the rubble now exposed it is a mixed blessing; details previously hidden are now visible, but some of the subtle signs of construction are being eroded and destroyed. While the beach was very busy, the winter sun low in the sky and the tide fast approaching at the time of my visit, I hope the selection of images have captured sufficient detail to both record the preservation of the remains and also identify and interpret some of the debris.

Interpretation

It’s important to remember that this pillbox has moved considerably since being constructed. It was likely set back into the dunes, and elevated to a certain degree, but erosion has changed the landscape beyond recognition to the 1941 builders. How far back it sat and how high I am unable to ascertain without contemporary plans or images. It is also not possible to establish what other defences may have been constructed around the pillbox, such as trenches, barbed wire entanglements or infantry positions.

However, having written an article recently on the construction of pillboxes, it gave me a better understanding of the techniques may have been use when constructing the Murlough Beach box. What it is often not possible to see is the base or foundations of a pillbox, and in the case of Murlough Beach these are clearly visible.

In image 1 (below) there is evidence of some corrugated iron sheet in the foundations, which has been secured up with wooden stakes of which one is still in a good state of preservation. The wooden stake is now within the concrete fill of the foundations, indicating that due to the difficulty of digging foundations in sand, a foundation trench was dug, shored up with corrugated iron and then filled with concrete. In more solid ground conditions this wouldn’t be necessary.

Image 1: A medium shot of the debris that shows the relationship between the foundations and walls (2021 © Author)

There is a steel plate inside the box which based on evidence from other pillboxes I think may be the external steel door. This hadn’t previously been identified in the previous survey, and appears too long to be an internal loophole shutter.

The internal floor of the pillbox has broken away, and may only have been s thin crust of concrete laid on the sand. It is possible that one of the slabs sitting inside the box may be part of the floor, and as the sand has eroded and support fallen away the floor has crumbled.

Also in image 1 (above) there is evidence in the manner in which the pillbox walls were constructed. Impressions on the walls from the wooden formwork are still evident. A wooden mould would have been constructed by carpenters that formed the shape of the pillbox. Much like a box, both an internal wall and an external wall would have been constructed, before the locally mixed concrete would have been poured into the moulds. They could only be removed after the concrete had cured, or set. This would typically be around 10 days (if the concrete is over 6 inches thick) from the initial pour.

One point of observation from the remains of this pillbox is the apparent ease at which it has broken apart. Regardless of the means of demolition (mechanical, erosion, explosive), this pillbox has formed very distinct sections upon its demise. Having seen other pillboxes that have been demolished, or attempts have been made, a cohesive reinforced concrete structure does not, and should not, come apart like this. UAS hypothesised that the pillbox had been explosively demolished, I will look more at this later.

The sectional appearance of this box comes from the manner in which it was constructed; the concrete was not poured continuously which has resulted in each pour of concrete creating a distinct new layer which has then apparently separated with relative ease. This poor cohesion is seen in the inlayed section of Image 2 (below). Attempts have been made to increase adhesion between concrete pours by adding keystones in the layer laid first (Image 1 above), so that when a subsequent layer is poured on top it binds to the key as well as the surface of the concrete. There are many reasons for not pouring at once, perhaps resources, tides or weather.

Image 2: Looking in the same direction as Image 1 but further back from the debris, some further wall sections can be observed (2021 © Author)

Also in Image 2 (above) are a couple of features that give us a reminder of the true purpose of the pillbox. I am confident that the features highlighted above are a loophole and the angled recess below is a feature in many pillboxes for the front leg of a machine gun tripod. These features are seen in other pillboxes nearby.

With the concrete eroded by the sea, this has left the core of the pillbox visible. As well as cement, an aggregate is used in the construction of concrete. The quality of this aggregate is important to maintain the integrity and strength of the concrete, especially where it must withstand the rigours of a sea-bourne attack. In a 1939 document for engineers, the aggregate Aggregate “can be any granite, gravel, crushed ballast or other sound and hard material, free from impurities. Pit gravel or river ballast can be used as a substitution for a sand and stone mixture, but must also be free of impurities.1War Department schedule of prices for works and repairs to buildings, 1939” Upon close inspection of the aggregate used in this pillbox (Image 3, below), it not only appears not to be as course as would be expected (with consideration given to erosion of exposed faces) but the girt size and density is greater than many other pillboxes of the time.

A larger aggregate has been used for the foundations as has been used in the walls of this pillbox.

Image 3: Exterior surface of the pillbox showing the core of aggregate (2021 © Author)

Looking more closely at the debris to the front of the pillbox, we can identify some more components of this pillbox. The roof slab, a thinner, larger piece of concrete is sitting out to the front, and another wall section has collapsed, showing the continuation of a corner.

In this section, which has been more greatly eroded by the sea, reinforcing steelwork is appearing through the surface. With a continuously poured pillbox with high quality concrete, the reinforcing steelwork should help bind the structure together and spread any loads across the structure. At this stage I am unsure if the reinforcing extends to the whole structure, or is just present on the front walls and roof slab. From the 2008 visit photographs there are signs of some reinforcement extending between two sections, but only a single plane of steel, as opposed to a three dimensional framework that would be expected.

Image 4: Debris to the front of the pillbox showing signs of reinforcement (2021 © Author)

To demonstrate the technique of constructing a reinforced concrete pillbox wall, I have drawn a diagram (below). First a steel wire frame is constructed, likely tied into a foundation section. Around this is constructed a wooden formwork which is supported by wooden stays and tie wire to prevent the walls separating under the weight of wet concrete when it is poured. This formwork would be the entire shape of the pillbox walls, excluding roof. The concrete would then be continuously poured into the top of the formwork, until at the desired level for the walls. It would then be left for 10 days to cure before the formwork would be removed.

Technique of constructing a reinforced concrete wall 2021 © Author

From what is observed in Image 4 (above) it appears as if only a single layer of wire reinforcement was placed into the concrete walls. Either as a result of inexperience or a limit on the resources available.

There is other metal work visible in the remains. Not only does reinforcing steel appear, but there are recognisable elements from the fixtures and fittings. Image 5 (below) which shows one of the simple rectangle loopholes also has some signs of the metal rail that would have once adorned the top and bottom of each loophole to accommodate a metal shutter; less for protective purposes more to weatherproof the pillbox.

Image 5: Loophole and evidence of fixtures (2021 © Author)

Finally, Image 6 (below) shows what was once the door closure and straight edge of the door opening. The door would have been a reduced size aperture at the back fo the pillbox, protected by a simple sheet steel door on hinges, that had a closure mechanism to secure the door from the inside.

Image 6: Door closure fitting on a concrete slab to the rear of the box (2021 © Author)

Challenging the 2001 report

“The WWII Pillbox at Murlough, County Down appears to be hexagonal in design and this would give it the official designation of FW3/22.”

In this condition, it is very difficult to establish the typology of this pillbox. The report identifies the remains as coming from a Type 22 pillbox, being hexagonal in shape. The Type 24 pillbox is also a hexagon, but with a wider rear wall and differing corner angles (image below).

Pillbox type comparison. Both the Type 22 and Type 24 are six-sided, with the Type 22 being a true hexagon and offering a slightly greater amount of rear protection. Depending on the siting of the pillbox, the Type 24 can offer a great amount of enfilade (flanking) fire, such as that along an open stretch of beach.

With Type 24 or variant pillboxes cast in concrete surviving nearby at Newcastle and Ballykinlar, it is possible that this example may also be a Type 24. And with a requirement to provide flanking or enfilade fire along the beach, a Type 24 would be appropriate.

Without further research and measurement I can not confirm either type.

“the presence of angular stones and not beach-rolled pebbles in the fabric of the other structural components indicates that these were not constructed on the beach, but were transported to the site and erected, using a pre-fabricated design.”

For reinforced concrete design it is not advisable to use beach-rolled pebbles. Not only would they have to be washed in freshwater before use, but the cohesion of soft edged aggregate is far inferior to that from angular stones. Aggregate would have been transported to location for use in pillbox construction. Even the use of sea sand in the manufacture of cement was prohibited by the War Department, with special permission required if there was no alternative, and even then any sea sand must have been washed with fresh water prior to use.

During the Second World War there were various pillbox designs that were implemented and constructed across the UK, including prefabricated variants. There are many examples of these around the south of England, but none remain in Northern Ireland to the best of my knowledge. Even these prefabricated variants consisted of concrete panels filled with a core of concrete. Ordinarily, a pillbox was constructed with either temporary wooden, corrugate iron or brick formwork (also known as shuttering), with a core of cast concrete. The benefit of using pre-formed or prefabricated shuttering was the time saving in construction as opposed to fabricated wooden moulds which into which the concrete was then cast.

There is no evidence that this pillbox utilised any pre-fabricated components. All components for the manufacture of this pillbox, and all others, were required to be transported to site; including wood for the formwork, scaffolding, steel reinforcement, tie wire, coarse freshwater aggregate, sand, fresh water, steel fixtures and fixings, tools and manpower. From start to finish I would have expected the construction. of this pillbox to take around 2 weeks (including the 10 days for concrete curing).

“Within the remains of the Pillbox were a number of iron items, some partially buried in the debris. It is difficult to determine accurately their function.”
Interior metalwork and machine gun leg recess at the pillbox nearby on Tyrella Beach

From the 2008 and 2021 visits I have been able to identify a number of steel items:

  • Reinforcing steelwork
  • Steel door
  • Door closure
  • Loophole shutter rails
“This Pillbox at Murlough is comprehensively damaged, with every wall section shattered and its roof lying inverted to the south, strongly suggesting that it was destroyed by explosives. This was most likely carried out by the military during the recent civil disturbances in Northern Ireland, to prevent its use by terrorists to attack the nearby Ballykinler Army Camp.”

Murlough has been “owned by the National Trust and managed as Ireland’s first Nature Reserve since 19672National Trust website“. As a nature reserve, it may have been sought to destroy this man made obstruction and let nature take over. If may have been demolished at this stage, or for this purpose. However, I want to think more about the theory the UAS put forward.

During the height of the Troubles there were many locations that were indeed destroyed by the Army to prevent them being taken over and used by terrorists to attack security forces. I have recorded a number of pillboxes that have been demolished, or attempts made to demolish them, manufactured to the same (theoretical) standard as this; reinforced concrete. Explosive demolition is violent, and serious damage occurs, with the shattering effect of the explosive causing harsh fractures in the concrete, fragmenting other areas and bending or twisting steel. Acknowledging that many years have passed since this pillbox was demolished, I do not think that it was explosively destroyed.

Another task that I carried out was to attempt to assess the risk that a pillbox in this area would have posed. In the aerial image below, I have placed the pillbox and a series of range rings emanating from it. The pillbox was only designed for light weapons; machine guns or rifles. And with limited range, and no line of sight to the main camp at Ballykinlar or barracks at Abercorn, the Murlough Beach pillbox would have been out of range for many of the regional terrorist groups weapons. It was also not their method to mount attacks from fixed positions. With two pillboxes remaining intact on the edge of the camp itself, both of which are accessible from the public road and farmland, I am doubtful of the theory that it was destroyed to prevent use as a firing position.

Aerial image of Ballykinlar including the location of the Murlough Beach pillbox and labelled range rings from the box © Google Earth 2020

Conclusion

The pillbox at Murlough Beach, even though destroyed, can shine some light on the methods used when constructing such defences. In combination with the remaining beach defences nearby, a good picture of the defensive landscape can be built up, of which this pillbox was key.

As the remains slowly dissolve into the seascape, it seems clear that the construction was not as textbook as might have been expected. The lack of cohesion between concrete pours, the large aggregate used in great quantities, the lack of a rigid steel reinforcing framework, and the apparent ease at which this the box has succumb to natural forces lead me to think that this box was not constructed to the same standards, by the same contractors, or at the same time as the others in the area which stand strong 80 years after their construction.

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