The concrete pillbox on Bromborough Road was just one of many defences set up around Wirral in case of an airborne invasion from the Germans during WW2. The pillbox was placed strategically to defend the road in from the New Chester road and surrounding railway stations. The New Chester road was itself defended by two separate pillboxes on either side. The Spital pillbox is hidden away tucked behind an old wall and would have been hard pressed to spot until the soldiers had come around the corner straight into the line of fire.
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.