- As added protection for the occupants, the section trenches at Walberswick were provided with pillboxes. The particular form of these concrete defences is well known to those with an interest in the subject: those at Walberswick are of a type known as the 'Suffolk Square' due to their distinctive shape.
- Their distribution corresponds to the activities of 558 Field Company Royal Engineers, who were based at Theberton Hall, a few miles to the south of Walberswick in the summer of 1940.
- The Suffolk Squares were designed to protect their occupants against small arms fire only; with a wall thickness of 38cm they were not hardened 'shell proof' structures.
- They have exterior dimensions of 3.8m and internally are 3.1m square with a height of 1.94m. There were two loopholes on each of three walls with just one at the rear.
- Wall materials vary slightly but at Walberswick the exterior walls were built of three-inch concrete blocks and internally with standard stock bricks. The space between was filled with concrete and it is probably that reinforcing steel rods were only used at the corners.
- The loopholes were of prefabricated concrete and inserted during building. Concrete shelves under the loopholes allowed riflemen to rest their elbows when firing. Perhaps alarmingly for the occupants, there was no anti-ricochet wall to prevent incoming bullets spinning around the interior.
- The roof and floor were constructed of a concrete slab about 30 cm in thickness and the entrance was protected by an anti-blast wall splayed in order to give an improved arc of fire from the rear loophole.
- Where earthworks exist on the ground or where their presence can be seen from aerial photographs, the pillboxes at Walberswick were often part of wider trench systems.
Suffolk Square Pillbox at Walberswick. This pillbox is now in a private garden and has been painted green in order to aid its new function as a garden feature. The coat of paint helps to show the crude construction from concrete blocks.
Rear View of a 'Suffolk Square' pillbox at Walberswick. The loophole was to dispatch any intruder attempting to gain entry. There is little evidence for doors in the pillboxes in this part of the county; the likelihood is that they were always open to the rear.