Answer:
Twenty years after the glory days of the Round Table, when King Arthur and his original knights are middle-aged, Sir Lancelot of the Lake is summoned in the name of King Pelles, the Grail Keeper and Fisher King, to knight Galahad, Lancelot's son conceived by a trick of Pelles's daughter Elaine.
Merlin became involved in the conception of Arthur, when Uther fell in love with Duke Gorlois' wife, Igraine. Gorlois (Hoel) was duke of Cornwall, and he was one of Uther's allies in the war against the Saxons. Gorlois was offended when he saw that Uther could not control his feeling for his wife.
