AndrewMcBurnie

Hi, thanks for the comment. You're the second person to mention being reminded of the Guild Navigators from "Dune".  I don't know whether it influenced my thinking or not; I first thought of the Walkers in a note I made in about 2009. 
          I enjoyed Dune, but I always found it difficult to accept the idea of a medieval style aristocracy, with "Dukes" etc, existing in a presumably advanced, technological society.