As King Charles III hosts Donald Trump for his second UK state visit, expect pomp, protocol and perhaps even meme-worthy missteps. If there's one word that springs to mind when one hears "state visit," it's probably "protocol." Especially when it involves the House of Windsor, whose namesake castle is where King Charles III will host US President Donald Trump during his second state visit to the United Kingdom this week. This had been avoided on his previous state visit, as security logistics were deemed too complex for the event held in London. To be clear, state visits are extended by the British monarch on the advice of the government.