I read Sharon Kay Penman's Welsh trilogy alongside Alison Weir's biography of Eleanor of Aquitaine, and those books started my interest in medieval England. Eleanor was a supporting character in Here Be Dragons (her granddaughter, John's illegitimate daughter Joan, married Llewellyn of Wales), and she's the center of one of the plot threads in Time and Chance. Her marriage to Henry II provides one of the plot threads in this sprawling novel, the compelling and sometimes explosive relationship between two intelligent and strong willed leaders which is eventually destroyed not by Henry's affairs but the fact that he falls in love with one of his mistresses. Losing Eleanor's affection also means that he loses her shrewd political advice (the one time he goes against her counsel is when he nominates Thomas Becket to be Archbishop of Canterbury), and eventually leaves Henry alone in the political crisis of his own making.
Penman's usual style is to make a minor (or, in this case, fictional) member of the court a major character through whose eyes we see the plot. In this trilogy, she gave Henry I an extra son (with 20 known illegitimate children, who's going to notice another one) named Ranulf. Raunulf's mother was Welsh and in While Christ and His Saints Slept, he married his cousin and serves and a bridge between the two countries, as well as being the voice of reason to his nephew, Henry II. Penman masterfully twines the two plot threads, but Ranulf's story frequently refers back to the prior novel and at times, I felt that I needed to check While Christ and His Saints Slept to fully understand Time and Chance. Still, I enjoyed the novel and it's evocative descriptions of medieval court life - I just recommend reading the trilogy as more of a unit than three separate entities.