The legend of King Arthur's queen Guinevere and her fatal love for the knight Sir Lancelot was extremely popular in the Middle Ages when most people had arranged marriages, even peasants. Although the Cathar-influenced troubadour culture in the south of France tended to glorify love outside of marriage, the basic plot of the legend is that adulterous romance has heavy consequences. The dalliance of Guinevere and Lancelot led to the destruction of Camelot and ruined many people's lives. According to the old legends, both Lancelot and Guinevere entered monasteries and ended their days in prayer and repentance.
The story was taken up by subsequent generations. Although Tennyson captures the intoxication of the initial infatuation in one of his poems, he also shows the many tears and repentance after disaster has overtaken the lovers and the kingdom.
Here is an excerpt from Tennyson's "Sir Lancelot and Queen Guinevere:"
Then, in the boyhood of the year,Share
Sir Launcelot and Queen Guinevere
Rode thro' the coverts of the deer,
With blissful treble ringing clear.
She seem'd a part of joyous Spring;
A gown of grass-green silk she wore,
Buckled with golden clasps before;
A light-green tuft of plumes she bore
Closed in a golden ring.
Here is Tennyson's rendition of the queen's repentance.