Bugbear, the Pendragon Cycle is a series of books centered around Arthur and Merlin, but in a more "historical" setting, albeit with fantasy elements. Merlin is a Christian Druid, Arthur is a British chieftain, etc. The series is set in the 5th century; Hadrian's wall is still the main defense against the "barbarians" to the North, but the incursion of "Saecsens" is another issue.

Then there's the Atlanteans, but that's a whole 'nother thing.

All in all they are well written books but not what some people expect if they only know the popular stories of Arthur and Camelot. Heck, Arthur doesn't even enter the story until the third book. The first one is about Merlin's father lol!