Naval constructors could read secrets in plain sight

The Anglo-German Naval Agreement created opportunities for British observers to see German shipyards while trying to draw Germany into a treaty system. Naval intelligence did not always require covert espionage because experienced constructors could recognize when visible dimensions, hull lines, or yard activity did not match official explanations. Italian cruisers entering British ports for emergency work offered an even closer chance to test prior estimates. Specialists who spent their careers designing and building ships noticed inconsistencies that could remain invisible to a general visitor. Open sources became valuable intelligence when the observer knew exactly what a compliant design and an ordinary shipyard should look like.