The design of the castle may also have alluded to Arthurian mythology, which were a popular set of ideals and beliefs among the English ruling classes at the time. Thomas appears to have had an interest in the Arthurian legends, and used the pseudonym "King Arthur" in his correspondence with the Scots. Dunstanburgh, with an ancient fort at its centre encircled by water, may have been an allusion to Camelot, and in turn to Thomas's claim to political authority over the failing Edward II, and was also strikingly similar to contemporary depictions of Sir Lancelot's castle of "Joyous Garde". Dunstanburgh Castle has been closely associated with the legend of Sir Guy the Seeker since at least the early 19th century. Different versions of the story vary slightly in their details, but typically involve a knight, Sir Guy, arriving at Dunstanburgh Castle, where he was met by a wizard and led inside. There he comes across a noble lady imprisoned inside a crystal tomb and guarded by a sleeping army. The wizard offers Guy a choice of either a sword or a hunting horn to help free the lady; he incorrectly chooses the horn, which wakes the sleeping knights. Sir Guy finds himself outside Dunstanburgh Castle, and spends the rest of his life attempting to find a way back inside. It is unclear when the story first emerged, but similar stories, possibly inspired by medieval Arthurian legends, exist at the nearby locations of Hexham and the Eildon Hills. Matthew Lewis wrote a poem, "Sir Guy the Seeker", popularising the story in 1808, with subsequent versions produced by W. G. Thompson in 1821 and James Service in 1822. The tale continues to be told as part of the local oral tradition. Several other oral traditions about the castle survive. One of these involves a child prisoner within the castle, who escaped, throwing the key to her dungeon into a nearby field, sometimes argued to be an outcrop of land north-west of the castle, which from then onwards was infertile. Another centres on a man called Gallon who was left in charge of the castle by Margaret of Anjou and entrusted with a set of valuables; captured by the Yorkists, he escaped and later returned to reclaim six Venetian glasses. The historian Katrina Porteous has noted that in the 14th century there are records of receivers and bailiffs at the castle called Galoun, potentially linked to the origins of the Gallon of this story. There are local stories of tunnels stretching from Dunstanburgh Castle to Craster Tower, Embleton and Proctor Steads, as well as a tunnel running from the castle well to the west of the castle.