Britain's thin coastal defenses before the First World War

What coastal defenses did Britain have immediately before and during the First World War?

Some batteries remained, mainly with 6-inch and 4-inch guns, but they were too weak to defeat a major German raid until wartime reinforcement.

The prewar coastal-defense system is described as badly atrophied rather than entirely absent. Scattered 6-inch and 4-inch guns were insufficient against the kind of force Germany could send across the North Sea. The panel contrasts this with the concentration of heavy guns at Singapore and asks how 15-inch batteries around Dover and Folkestone might have changed German passage through the Channel. The alternative northern route would still expose raiders to Royal Navy forces operating from Scapa Flow.