Re: What is true in history?
A lot of these old stories are an amalgamation of several, though, plus a good dollop of myth.
The Robin Hood story can be tied in with the Jack in the Green / Green Man/ Cernunnos tales, as well as stories of other British Outlaws.
So what you get is a story that takes on a life of its own.
A good book on this is `Hero with a Thousand Faces` by Joseph Campbell. In it he shows how certain myths or tales re-occur through different cultures and times.