The first thing I thought of when I saw the lion tattoo was Richard the Lionheart but I agree that it is much more likely they’ll relate Robin to King George than to an historical figure like Richard. Now I want to see that story!
By the way, those who are fans of historical fiction might enjoy the trilogy of novels by Sharon Kay Penman which tell the story of Eleanor of Aquitaine, Henry II, Richard Lionhart and other members of that bunch. The books are:
When Christ and His Saints Slept (Stephen of Blois, Empress Maude)
Time and Chance (Henry II, Eleanor, Thomas Becket)