The link below is to an article I wrote for the Dorothy Dunnett Society's publication Whispering Gallery. The article is titled "Blyth Spirit: Unlocking Jerott's Innermost Door," and it sprang from Checkmate, Part III, Chapter 2.
Be forewarned that if you have not read Checkmate, this article will be filled with SPOILERS. If you don't know who Jerott Blyth is, this article is definitely a spoiler fest!