Just to make it explicit: Other than single stanza, there is no authentic text of this ballad. (Some modern may have recreated it, but there is nothing from tradition.)

Hardly surprising, for a fourteenth century event. Few songs last that long, and if it had still been around in the nineteenth century (which I doubt), the nineteenth century text would have had to be very different from the original.

I'm personally not convinced that it was ever an actual song, but it hardly matters. :-/