What is an example from The Once and Future King by T. H. White that illustrates the Arthurian idea of courtly love?
One example of Arthurian courtly love in White's tale occurs when Wart proclaims to Merlyn that were he a knight errant he would not wed (he thinks wives stupid ...) but would have a lady love whose "favours" he would wear in his helmet when he fought for glory and honor. Arthur Conan Doyle's novel White Company sheds light on the idea of "favour" when the hero takes his lady's scarf with him into battle. Thus this favour that Wart would wear in his helmet would be something like a hankie or other gift of lace or satin or silk.
"I shall have to have a lady-love ... so I can wear her favour in my helm, and do deeds in her honour."
Another brief example of Arthurian courtly love involves Lancelot and Queen Guenever. The lady's honor was an important part of courtly love. In other words, a lady may give her affection and even her favors to a knight who admires her, but honor requires that the boundary of physical affectionate must never be crossed. Even after his adventures lead him to wander the forests; after he slays Carados; and after the witches abduct him, Lancelot still insists upon and vouches for Queen Guenever's honor:
"[What] you say about me and the King's wife of Britain is untrue. Guenever is the truest lady unto her lord living."