There's a large variety of accounts of the legend. People have been retelling and reimagining this story for a thousand years. I've seen two new movies and a tv series in the past few years. Patrick Stewart has been in at least two retellings. There isn't exactly a canon for the story. So, I should have said it's exactly what happened to King Arthur in some of the stories I've seen.
Even if Mallory's work was the canon that Jim must, by royal decree, work from, it's close enough to create a parallel. He was taken there by a Queen, a Valkyrie, Murphy (who the ancient prophesies say will one day become Mab through time travel shenanigans), and with the assistance of Molly, a fairy queen.