King Charles has done two things simultaneously this week that reveal much about what kind of reign he aspires to. First, he has led the nation in the ritualising of its sorrow - a sorrow that has been quietly expressed and subdued but it is nonetheless real. And second he has signalled to us in the clearest terms possible that this is a reign that will put the future of the Union - the integrity of the United Kingdom itself - at the heart of its concerns.