Deterring invasion without violating Belgian neutrality

How could Britain deter a German move through Belgium without first violating Belgian neutrality itself?

Britain could guarantee Belgium publicly and prepare troops and transports for immediate entry only if an invader breached that neutrality.

The question notes that neutral Belgium could not simply admit British troops in July 1914. Britain could publicly guarantee Belgian neutrality while assembling troops, transports, and supporting arrangements close enough to react quickly after any invasion. Advance talks, exercises, and logistical preparation could reduce the delay without placing a foreign force inside Belgium beforehand. A later suggestion adds infrastructure and logistics advisers as a peacetime way to prepare movement routes without stationing combat forces in Belgium. The distinction matters because deterrence can rest on unmistakable readiness even when legal and diplomatic limits prevent forward deployment.