Lancelot of the lake (1974)

Having failed in their quest for the Holy Grail, the knights of the Round Table return to Camelot, their number reduced to a mere handful. Seeing a rift developing between Lancelot and Mordred, Arthur urges his knights to bury their differences and become friends. However, the king is unaware that Lancelot is having an affair with his queen, Guinevere. Lancelot is torn between his duty to his king and his love for the queen, whilst Mordred is determined to use his infidelity to destroy him.