I wonder if "Lancelot" is close?

Although he generally represents the very model of knightly chivalry, his adulterous love for Guinevere tarnishes his image somewhat. It contributed to the failure of his quest for the Holy Grail, the collapse of the fellowship of the Round Table, and the death of Arthur.

Mmm. Not quite right. I'll keep looking....

Let us go in peace to love and serve the board.