President Trump will make a two-day state visit to Britain from Sept. 17 to 19, Buckingham Palace confirmed on Sunday, making him a rare head of state to be accorded a second such visit. King Charles III will play host to Mr. Trump and his wife, Melania, at Windsor Castle, the palace said in a statement. The king issued Mr. Trump a formal invitation last February in a letter presented to him by Prime Minister Keir Starmer during a visit to the Oval Office. The queen threw him a lavish banquet at Buckingham Palace and gave him a royal artillery salute. But Mr. Trump picked a fight with London’s mayor, Sadiq Khan, who is Muslim, just before his arrival, calling him a “stone cold loser” on social media and accusing him of doing a terrible job of running Britain’s capital city.