King Arthur is a legendary British figure whose story was developed in a number of medieval romances. Being in the public domain, he has inspired stories from a ragne of comic publishers.
In the fifties, Frank Bellamy drew a strip for Swift entitled "King Arthur and his Knights". There have also been many comics which, while not using King Arthur himself as the main character, have used Arthurian legend as a backdrop. "The Combatants" from Tina starred the daughter of an Arthurian knight, and Attic Brand published a magazine tying in with the BBC series Merlin, containing a strip featuring younger versions of Camelot's denizens.
Various time travelling characters have ended up in the era of Camelot; examples include Adam Eterno and Gertie Grit. Meanwhile, Captain Britain, a character created by the America publisher Marvel for a British readership, had an origin story inspired by Arthurian legend.
Of course, there have also been numerous parodies of Arthur and his knights. These include "Sir Laughalot" from Topper, "King Arthur and his Frights of the Round Table" from Whoopee, "The Nits of the Round Table" from Valiant and "Arthur! And his Square Knights of the Round Table" from TV Comic (based on an Australian television cartoon).