Was Robin of Locksley ever a real nobleman? If so, how much of the legend is true? Did he fight in the Crusades and return home to total corruption? Is the character of Prince John accurately portrayed as such an immoral character? Was Robin of Locksley actually a vigilante called Robin Hood having a fling with Maid Marian?

And if it's totally just a legend, what are the origins? When/ where was it started and why is it still so popular today?

Also, any suggested reading on Robin Hood would be hugely appreciated!