The Battle of Camlannis is King Arthur's final battle, in which he is mortally wounded by his his nephew Mordred. The story recalls that Arthur and his forces were away in Europe fighting (according to earlier sources) Emperor Lucius or (according to later sources) fighting Lancelot. When Arthur landed back in England, a series of battles ensued that climaxed with the Battle of Camlann. Both Arthur and Mordred are mortally wounded in this battle, but Arthur's army triumphed in the end.
While Camlann, Arthur's last battle, is not part of the battle list, it was a battle that was fought in Britain. The battle of Camlann is first mentioned in the Annales Cambriae (ca. 960-980). The name Camlann has a number of possible locations. It is said to have taken place by a river, and the prefix Cam means crooked. The battle probably took place, then, near a crooked river.
Various stories differ on how the battle started. Geoffrey of Monmouth's account is of a normal battle--both sides lined up and then charged into battle. In many other sources, though, the battle is set of by misunderstanding. Malory makes the beginning of the battle a complete misunderstanding: A knight is bitten by an adder, he draws his sword to kill the snake, and when others saw his drawn sword a battle resulted by mistake.
The Battles of King Arthur