The concrete pillbox at Bromborough Pool was built to defend Thomas Brasseys New Chester Road. It is just one of many defences set up around Wirral in case of an airborne invasion from the Germans during WW2. Two pillboxes occupy the high ground and were built on either side of the road to allow for a deadly arc of fire for any approaching vehicles.
One of the areas for most variation in design of these pillboxes on Wirral can be found in the shape of the Loopholes and the internal provision of weapon rests. There appears to be no hard and fast rules but the norm for the Type 22 Pillbox, essentially designed for use by riflemen, is to have Loops splayed to the outside. Some of these Loops are sometimes found to be complete per-fabricated units anything upto two feet square (60 x 60cm) simply inserted into the framework. In other cases the splay is formed by bricks or by shuttering giving a concrete Loophole; often both will have a per-formed concrete lintel, and some have projecting sills. A further example consists of a stepped splay where per-formed concrete blocks are used as one-piece steps.
Loopholes were sometimes furnished with flip-up shutters of wood or asbestos, or with steel shutters pivoting vertically. The provision for the rifleman to rest his elbow and ammunition clip is usually a wooden shelf mounted on iron bars built into the wall a little below the Loophole. Some of these shelves were hinged. However, many Type 22 Pillboxes are so crudely built that Loopholes are little more than holes in the wall, wider on the outside than on the inside.
This type of pill box is known as the type 22, it is a regular hexagon in shape with an embrasure in five of the sides and an entrance in the other. The embrasures are suitable for rifles or light machine guns. Some have a low entrance that allows an extra embrasure above. Each wall is about 6 feet (1.8 m) long and it was generally built to the bullet proof standard of 12 inches (30 cm) thick, although 'tank-gun proof' versions with walls around 1 m thick were also built (e.g. the granite and concrete examples on the Cowie Line in Kincardineshire). Internally there is a Y- or T- shaped anti-ricochet wall (the top of the Y/T nearest the entrance), the internal wall also helps support the roof. The type 22 is the second most common pillbox type with 1209 recorded as being extant. It is easily confused with the common type 24 which is an irregular hexagon and the less common octagonal.