The first and the most trusted knight of King Arthur is Sir Lancelot, who fell in love with the Queen of Camelot Guinevere.
Step-by-step explanation:
Guinevere was kidnapped by the Prince Malagant since he wanted to possess her land. Lancelot rescued her from her attackers twice and also won her heart.
King Arthur after knowing about this betrayal felt angry on his wife and knight. He died during his war with the Malagant. After his death, the queen Guinevere locks herself inside the church and refuses to see Lancelot again.