Trump Begins Europe Trip in BritainU.S. President Donald Trump is in Britain for a visit that includes meeting with the royal family, a state dinner and talks with outgoing Prime Minister Theresa May. Britain's Queen Elizabeth greeted Trump and his wife Melania after they arrived at Buckingham Palace by Marine One helicopter Monday. After a welcoming ceremony that included a 41-gun salute, and inspection of the Royal Guard of Honor, the Trumps headed inside for a private lunch with the queen. The queen gave the president and the first lady a tour of the picture gallery of the Buckingham Palace. The artifacts on display include an 18-century map of New York and a pewter horse statuette that the president gave Queen Elizabeth on his working visit last year. Before leaving Washington, Trump said his trip would be "very interesting" and that he thinks the United States and Britain have an opportunity to work out a "very big trade deal" in the near future. His visit comes as Britain is in the midst of political turmoil. Prime Minister May announced last month she would be resigning on June 7, two days after Trump’s departure, after failing to complete Britain's exit from the European Union. That process will be inherited by her successor, with no clear path to a resolution among sharply divided parties. Trump has publicly backed former foreign secretary Boris Johnson as leader of the Conservative Party to succeed May. He told reporters before departing the White House late Sunday he may meet with Johnson and Brexit party politician Nigel Farage while he is in London, potentially creating an embarrassment to the outgoing prime minister. What is certainly not on his agenda is a meeting with London Mayor Sadiq Khan, who wrote in The Observer newspaper that welcoming Trump for a state visit is "un-British." He cited Trump's sharing of tweets from a "British far-right racist group," the president's rejection of scientific evidence of climate change, and Trump "trying to interfere shamelessly" in the race to replace May. When asked if he would be open to meeting with Khan, Trump said Sunday, "No, I don't think much of him" and likened him to New York mayor Bill de Blasio, a Trump political opponent, “only shorter”.  Upon landing in London, Trump continued his attack on Khan via twitter, calling him a "stone cold loser" who "has been foolishly 'nasty' to the visiting President of the United States, by far the most important ally of the United Kingdom." Trump's trip will also include D-Day commemoration ceremonies in both Britain and France, and a stop in Ireland.