Editing Lancelot (section)

===Conflict with Arthur===
{{Further|Gawain|Mordred}}

[[File:SIR LAUNCELOT AND QUEEN GUINEVERE).jpg|thumb|left|[[James Archer (artist)|James Archer]]'s ''Sir Launcelot and Queen Guinevere'' (1864)]]

Ultimately, Lancelot's affair with Guinevere is a destructive force, which was glorified and justified in the Vulgate ''Lancelot''  but becomes condemned by the time of the Vulgate ''Queste''.<ref>Dover, ''A Companion to the Lancelot-Grail Cycle'', p. 119.</ref> After his failure in the Grail quest, Lancelot tries to live a chaste life, angering Guinevere who sends him away, although they soon reconcile and resume their relationship as it had been before Elaine and Galahad. When Maleagant tries to prove Guinevere's infidelity, he is killed by Lancelot in a [[trial by combat]]. Lancelot also saves the Queen from an accusation of murder by poison when he fights as her [[champion]] against [[Knights of the Round Table#Mador de la Porte|Mador de la Porte]] upon his timely return in another episode included in Malory's version. In all, Lancelot fights in five such duels throughout the prose ''Lancelot''.<ref>{{Cite journal |author=King, David S. |year=2016 |title=Victories foretelling disgrace: Judicial duels in the prose ''Lancelot'' |journal=South Atlantic Review |volume=81 |issue=2 |pages=55–71 |jstor=soutatlarevi.81.2.55}}</ref>

[[File:Tales of the Round table; based on the tales in the Book of romance (1908) (14580312508).jpg|thumb|Lancelot's bloody rescue of Guinevere from the stake in [[Henry Justice Ford]]'s illustration for Andrew Lang's ''Tales of the Round Table'' (1908)]]

However, after the truth about Lancelot and Guinevere is finally revealed to Arthur by Morgan, it leads to the death of three of Gawain's brothers ([[Agravain]], [[Gaheris]] and [[Gareth]]) when Lancelot with his family and followers arrive to violently save the condemned queen from being burned at the stake. During her rescue, the rampaging Lancelot and his companions slaughter the men sent by Arthur to guard the execution, including those who went unwilling and unarmed (as did Lancelot's own close friend Gareth, whose head he crushes in a blind rage). In Malory's version, Agravain is killed by Lancelot earlier, during his bloody escape from Camelot, as well as Florent and Lovel, two of Gawain's sons (Arthur's nephews) who accompanied Agravain and [[Mordred]] in their ambush of Lancelot in Guinevere's chambers along with several other knights from Scotland. In the Vulgate ''Mort Artu'', Lancelot's now-vacated former seat at the Round Table is given to an Irish knight named Elians.

The killing of Arthur's loyal knights, including some of the king's own relatives, sets in motion the events leading to the treason by Mordred and the disappearance and apparent death of Arthur. The civil war between Arthur and Lancelot was introduced in the Vulgate ''Mort Artu'', where it replaced the great Roman War taking place at the end of Arthur's reign in the chronicle tradition. What first occurs is a series of engagements waged against Lancelot's faction by Arthur and the vengeful Gawain; they besiege Lancelot at Joyous Gard for two months and then pursue him with their army into Gaul (France in Malory).

The eventual result of this is the betrayal of Arthur by Mordred, the king's bastard son (and formerly one of Lancelot's young followers), who falsely announces Arthur's death to seize the throne for himself. Meanwhile, Gawain challenges Lancelot to a duel twice; each time Lancelot delays because of Gawain's enchantment that makes him grow stronger between morning and noon. Lancelot then strikes down Gawain with Galahad's sword but spares Gawain's life (in the Vulgate, despite being urged by Hector to finish him off<ref>{{cite book | url=https://books.google.com/books?id=ojpHBAAAQBAJ&pg=PT17 | title=The Passing of Arthur: New Essays in Arthurian Tradition | isbn=9781317656913 | last1=Baswell | first1=Christopher | last2=Sharpe | first2=William | year= 2014 | publisher=Routledge }}</ref>). However, Gawain's head wound nevertheless proves to be fatal later, when it reopens during the war with Mordred back in Britain. Upon receiving a desperate letter from the dying Gawain offering him forgiveness and asking for his help in the fight against Mordred, Lancelot hurries to return to Britain with his army, only to hear the news of Arthur's death at [[Salisbury Plain]] (romance version of the [[Battle of Camlann]]).