Why German fleet building alarmed Britain

Why did German naval expansion create such a serious problem for Britain?

A German fleet near the British Isles required a major British response while Britain still had to maintain naval power around the world.

The strategic problem extended beyond Britain's ability to outbuild Germany. A large fleet immediately opposite the British Isles compelled Britain to respond, while the Royal Navy still needed forces for imperial routes and distant stations. Part of the miscalculation may lie with a Prussian political class accustomed to dictating settlements during German unification and after the Franco-Prussian War instead of negotiating among equals. German diplomatic flexibility also declined after Otto von Bismarck left office and Wilhelm II proved less controllable than older statesmen expected. In this interpretation, the attempt to build a fleet capable of challenging Britain turned a manageable rivalry into a direct strategic and political threat.