Lemongrove He doesn't need her permission, but if he is visiting part of a country of which she is First Minister and is planning to make political comments, then basic good manners demand that he drops her a line to say "By the way, I will be in Orkney on Thursday for a while. Sorry, but a busy schedule prevents me stopping off in Edinburgh to say hello." A note from one leader to another. A real leader would know that instinctively.
He is deliberately demonstrating that HE has precedence over her and can walk in unannounced whenever he wants to, like the bailiffs with a court order in their hand. It is a warning shot across the bows of devolution.