A news item today claims that German cycling tours of Britain in the years before WWII were actually covers for spying operations by Hitler Youth. My sister-in-law told me this story a while ago. She says they came to Tamworth in Staffordshire which is where I grew up.
I had intended to use this as the basis for a short story but, now that it is in the public domain, it won't have the same originality and impact.
Just goes to show - you should grab your opportunities when you can.