From French sources, Sir Thomas Malory, English writer in floruit in 1470, adapted Le Morte d'Arthur, a collection of romances, which William Caxton published in 1485.
From original tales such as the Vulgate Cycle, Sir Thomas Malory, an imprisoned knight in the fifteenth century, meanwhile compiled and translated the tales, which we know as the legend of king.
"Sir Launcelot, now I well understonde that thou arte a false, recrayed knyght and a comon lechourere, and lovyste and holdiste othir ladyes, and of me thou haste dysdayne and scorne. For wyte thou well, now I undirstonde thy falsehede I shall never love the more, and loke thou be never so hardy to com in my siyght. And right here I dyscharge the thys courte, that though never com within hit, and I forfende the my felyship, and upon payne of thy hede that thou se me nevermore!"
About two seconds after the Tale of the Sankgreal is over, Lancelot forgets all of that talking with God and priests and the Holy Ghost that he did on the road to becoming a better man and knight. He gets back to court and sees Guinevere, and they BRYNNE SO HOOTE for each other that his libido wins the day. Sorry God. So starts this tale.
In my opinion, this is a better written book of Le Mort d'Arthur than the Grail tale is. The Grail is more famous and it has more important prophecies and character development in it (in this book, there are basically two main takeaways: 1) Lancelot and Guinevere are still banging, and 2) Aggravain is pissed of as hell about this and will almost certainly be a total prick about it at a later juncture). But this book is easier to read, shorter, and backed with tighter action and less confusing religiosity.
I won't go into the different sections, but basically through all of them you get the sense that everyone knows about Lancelot and Guinevere (even Arthur, who wishes that Lancelot was at court with them to fight for the Queen at one point *cough*royalthreesome*cough*), but it's being kept in the sphere of the public unspoken, which is where it has to stay to be okay. Aggravain will surely screw all of this up in the next books of Le Morte. Way to go, man.