Arthur did not kill Lancelot, for Arthur died before Lancelot died.
Guinevere was married to King Arthur, so ruled over Sir Lancelot as Queen. Then, the two fell in love and had an affair, thus causing the Last Battle, in which King Arthur is slayed while trying to kill Lancelot.
King Arthur's best knight was Lancelot
King Arthur was king of Camelot, Guinevere was his Queen, and Lancelot was one of his Knights of the round table.
Sir Lancelot
Lancelot
King Arthur's best knight is Sir Lancelot.
Guinevere was the wife of King Arthur. Guinevere
king arther was married to Guinevere and she was cheating on him with Lancelot.
He slept with Guinivere.(Arthur thinks they do!)
Because Lancelot had a affair with Queen Guinevere
Lancelot
Lancelot