I can tell you when the idea for this story came to me. It was the fall of 2008. Why do I remember that?
The tiny seed that grew into this story was a mingling of two different TV shows that I was watching at that time. One was the short-lived New Amsterdam on FOX about a Dutch man who came to New York in the 1600s and was still alive today. The other show was Robin Hood on BBC America.
Those two stories mixed in that nether region between asleep and awake and voilà! Under the Ancient Oak: The Story of Robin and Marian was born.