what were the affects of sir lancelots affair with queen guinevere on kings arthurs court?

Answer 1

It was a break in the sacred trust and bond of honor that the knights shared with one another.

Answer 2

Well, the effect was many fold. During that time the the bards and trouvere were out singing about "Courtly Love" and that time an knight was allowed to champion another man's wife, but only chastely (in theory) but in actuality, a fair amount of hanky panky was going on. This affair affected Arthur in many was. As king, he could not be seen to the common man as being cuckolded (basically having his wife with another man) because he was a celtic king, and wordfame was very important to him. In actually celtic practice, they would have probably assigned a blush fine, and told them to knock it off. But Christianity was very anti-sex, especially old testament. And the Christian church could not have their representative tainted. Plus, Lancelot was Arthurs champion. So much so, that all duels, etc, were met by Lancelot...(officially) the greatest knight in the land. A celtic king is supposed to be perfect in mind, body and soul. So Arthur, regardless, was probably troubled. And that breaks that trinity. With the weakness this affair causes, now Arthur has a problem with his Celtic Enech (honor) his Christian standing, His army of knights, and his relationships with two of the people he loves. Mordred, and his cronies use this split to divide opinion, and throw Arthurs rule of law back at hime, and to break the area into factions. Galahad has not shown up yet to save the day. Arthur is damned if he does nothing, and damned if he punishes them. Ostensibly, if he had slain them out of hand, he probably could have kept his kingdom, but his good rep would have died with them. Instead, he tried to keep the middle course, and in the end, is sent to Avalon, to heal and await the final battle.