Child Ballad 31, "The Marriage of Sir Gawain", in which King Arthur is required to find out "what women most desire": Text of the original ballad
It has hundreds of verses (though not all have survived) and unfortunately, there is no known tune.

This won't be old enough for you, but I did a humourous, "modernised" 11-verse reworking of it: Sir Gav Gets Hitched that lasts 7 min 20 sec.
As it happens, the above-mentioned and brilliant Jon Loomes did the sound engineering and added lots of medieval-sounding accompaniment, and made it sound truly awesome...