British intelligence found out about Germany’s use of radar in World War II before they had seen any evidence of radar installations? Intercepted radio transmissions were found to repeatedly use the word “Freya”, which is similar to the name of the Nordic Goddess, Freyja.
Freyja had once enlisted the help of another Nordic God, Heimdallr, to help find her stolen necklace. Heimdallr was described as being able to “hear grass growing and single leaves falling” and “able to see to the end of the world” - this was the impetus they needed to send aerial photography missions over the French coast to find evidence of radar installations.