Back when fans first debated the concept of a possible Anakin, Padmé, and Obi-Wan love triangle at the root of the prequel trilogy's inevitable tragedy, the fabled King Arthur, Queen Guinevere, and Sir Lancelot triangle (as Star Wars already bore many parallels to Arthurian legend) was often used to bolster those arguments, especially as motivation for Anakin's transformation into Darth Vader.  These theories cast Anakin - as the central female figure's likely husband - in the role of Arthur, and Obi-Wan, the best friend and noble knight, as Lancelot.

However, when the individual characters are examined, Lancelot - the young, gifted, passionate Knight - far more resembles Anakin, while Arthur - the well-intentioned mentor and friend - more closely seems to parallel Obi-Wan.

In many tellings of the legend, Arthur willingly turns a blind eye to the lovers' involvement - as Obi-Wan appears to do with Anakin and Padmé - knowing that as King he would have to punish both his wife and best friend if the affair were made public. He ends up watching the world he's dedicated his life to serving collapse as a result.  Lancelot, as Arthur's most gifted Knight, becomes the Queen's champion, the Knight sworn to defend her life and honor.  His greatest temptation comes when he falls in love with Guinevere, a love that she will return - which will result in not only their downfall, but that of Arthur and his kingdom.

The talented, brash Knight and the beautiful Queen he champions - even at its most surface level the parallels to Padmé and Anakin are obvious.  It is an obligation to duty, an oath both have sworn to others - in Anakin and Padmé's case, it's the Republic and Jedi Order; in Guinevere and Lancelot's it is Arthur and Camelot - that makes a union between them impractical and forbidden.  For a time, Lancelot tries to escape his maddening passion for Guinevere, the torment the temptation of such feelings brings him - but soon both give in, embarking on a secret affair, stealing interludes with one another.  While sometimes tricked into bed by other women's sorceries, Lancelot's heart never belonged to any woman but Guinevere, and was always her defender whenever her loyalty or fidelity to Arthur was challenged.  Guinevere herself faithfully continued in her duties as Queen, refusing to leave her husband, whom she did love (but was not in love with).  In both cases, the pairs involved could have chosen to cast their duties aside and run away together, but instead choose to attempt to balance their forbidden feelings with their sworn obligations, knowing there would be dire consequences if they were discovered.

In some versions of the legend, the affair is discovered almost immediately.  In others, it goes on for years until they are publicly confronted.  In either situation, the public revelation of the affair - often by Arthur's wicked bastard son Mordred - is their downfall. Arthur is forced to banish Lancelot from Camelot, and sentence Guinevere to death for treason, though Lancelot rescues her, and she lives out the rest of her days in exile.  The conflict shatters Arthur's order of Knights when Arthur is pushed to declare war on Lancelot for his treachery with the Queen, a war in which Arthur and Mordred end up killing one another. And since his affair was with a married woman, it costs Lancelot the purity he would have needed to achieve the Holy Grail, which had been the ultimate quest for Arthur's Knights.

Though the pair themselves are doomed to misery, Lancelot himself does gain a small measure of redemption in the form of his son, Sir Galahad (the result of one of those tricked seductions).  Pure, chaste, and noble, Galahad succeeds where his father fails, achieving the Holy Grail.

[One other pair from Arthurian legend, Tristan and Isolde, also bears strong mythic parallels to Anakin and Padmé - another forbidden love between a knight and queen, which results in doom for both. Also, a semi-related bit of trivia: in a semi-recent film adaptation of the Arthur legend (in which the triangle is basically absent), Guinevere was played by Keira Knightley, who played Padmé's decoy in Episode I.]