London - Britain rolled out the royal red carpet for Donald Trump on Monday, with Queen Elizabeth leading the pomp and pageantry in honour of the U.S. president whose interventions into London's political crises threatened to overshadow the visit.
From a banquet with the 93-year-old monarch, who also gave him a guided tour of historical items at Buckingham Palace, to tea with heir Prince Charles, Trump and his wife Melania were to be treated to the full royal spectacle of a British state visit.
The three-day trip is cast as a chance to celebrate Britain's "special relationship" with the United States, boost trade links and reaffirm security cooperation.
But the proudly unpredictable 45th U.S. president's views on Britain's exit from the European Union, on the possible successor to Theresa May as British prime minister and a row over China's Huawei have cast a pall over the visit.
Even as he flew into the British capital, he reignited a feud with London Mayor Sadiq Khan - who had written on Sunday that Britain should not be rolling out the red carpet for Trump - describing the mayor as a "stone cold loser".
"London part of trip is going really well. The queen and the entire royal family have been fantastic," Trump wrote on Twitter. "The relationship with the United Kingdom is very strong. Great love all around. Also, big Trade Deal is possible once UK gets rid of the shackles. Already starting to talk!"
The state visit was promised by Prime Minister May back in January 2017 when she became the first foreign leader to meet Trump after he took office.
The first day of such a visit is customarily taken up with a series of royal engagements and ceremonies.
At Buckingham Palace, Melania - in an elegant, white below-the-knee Dolce & Gabbana dress with navy blue collar and belt and a custom hat by Herve Pierre - stood alongside the queen and Charles's wife Camilla, while Charles and the president inspected the guard.
After lunch with Elizabeth and other senior royals, the queen gave the Trumps a guided tour of artefacts of American historical interest from the royal collection. She also showed him some of her family's golfing memorabilia in a nod to the president who owns two Scottish golf courses.
The queen's second son Prince Andrew then accompanied him to Westminster Abbey, coronation church of English monarchs for 1,000 years where he laid a wreath at the Grave of the Unknown Warrior, before tea with Prince Charles at his home, Clarence House.
The day culminates with a lavish banquet at Buckingham Palace, where men wear white tie coats with tails and women evening gowns.
Away from the pageantry, Trump is set to make his trip the most unconventional state visit in recent British history.
He has already waded far into Britain's turbulent domestic politics, where more than a dozen candidates are vying to replace May, who announced last month she was quitting after failing to get her EU divorce deal through parliament.
Trump, who has regularly criticised May's Brexit tactics, said Britain must leave the bloc on the due date of Oct. 31 with or without a deal.
He praised May's Brexit-supporting rival, former foreign minister Boris Johnson, saying he would be a "great" potential prime minister and also called for arch-Brexiteer Nigel Farage, a scourge of May's ruling Conservative Party, to conduct talks with the EU.
Brexit is the most significant geopolitical move for the United Kingdom since World War Two and if it ever happens then London will be more reliant on the United States as ties loosen with the other 27 members of the EU.
At a meeting with May, Trump will also warn Britain that security cooperation, a cornerstone of the western intelligence network, could be hurt if London allows China's Huawei a role in building parts of the 5G network, the next generation of cellular technology.
The Trump administration has told allies not to use its 5G technology and equipment because of fears it would allow China to spy on sensitive communications and data. Huawei denies it is, or could be, a vehicle for Chinese intelligence.
U.S. Secretary of State Mike Pompeo told Britain last month it needed to change its attitude towards China and Huawei, casting the world's second largest economy as a threat to the West similar to that once posed by the Soviet Union.
Britain's relationship with the United States is an enduring alliance, but some British voters see Trump as crude, volatile and opposed to their values on issues ranging from global warming to his treatment of women.
Hundreds of thousands protested against him during a trip last year and a blimp depicting Trump as a snarling, nappy-clad baby will fly outside Britain's parliament during the visit.
Other protesters plan a "carnival of resistance" in central London and Jeremy Corbyn, the socialist leader of Britain's opposition Labour Party who declined an invitation to attend the state banquet, said he would join them.
Responding to Trump's latest criticism of the London mayor, Khan's spokesman said: "This is much more serious than childish insults which should be beneath the President of the United States. Sadiq is representing the progressive values of London and our country..."
Trump said instead of demonstrations, there had been "tremendous crowds of well-wishers".
"Haven't seen any protests yet, but I'm sure the Fake News will be working hard to find them," he said on Twitter.
Outside the palace, a handful of supporters sported "Make America Great Again" hats and "Trump 2020" shirts. A small number of protesters were also present.
The second day of Trump's trip will focus on politics, including a breakfast with business leaders, talks with May in 10 Downing Street, a news conference and a dinner at the U.S. ambassador's residence.Reuters