One thing that Moffat has introduced these last couple seasons is a poem/song about the Doctor's life. It began with the Silence and the "Tik tok goes the clock" rhyme, which showed up a couple times in Season 6. We also had River's narration of the "Demons run when a good man goes to war" poem. Now, in the most recent episode, we have the Whisper Men and their poem about the Doctor's death: "The man who lies will lie no more, when this man lies at Trenzalore." Now, I realize it's probably more for dramatic effect than anything, but I can't help wondering if, in the Doctor Who universe, all of these things might be part of a larger work. Dorium says that "Demons run" is a part of a very old saying, the oldest. But where did it come from? Who is the author is this Ballad of the Doctor?