This one is a bit more bawdy, and has more of an 18th C than 1960's feel. That isn't within a millennium of the actual Arthur, and is still three centuries away from Le Morte d'Arthur, but it sounds a bit more properly old.
The singer is Mordred, bastard son of King Arthur who is conniving for his throne. I imagine this tavern-style, getting up on a table to make fun of Galahad and all those seeking the Grail. I'm not including the lyrics, as I think it will spoil the effect.