He had only just landed on UK soil for a state visit laden with diplomatic peril... And the U.S. President was already courting controversy.
Donald Trump renewed his verbal attacks on London Mayor Sadiq Khan on Monday (June 3).
Calling him a "stone cold loser" after the mayor criticized the British government's decision to offer a state visit to the sitting president.
Posting on Twitter just before Air Force one landed in Stansted airport, Trump wrote: "@SadiqKhan, who by all accounts has done a terrible job as Mayor of London, has been foolishly 'nasty' to the visiting President of the United States, by far the most important ally of the United Kingdom.
He is a stone cold loser who should focus on crime in London, not me." Trump's interventions on Brexit, outgoing Prime Minister Theresa May's successor and a row over China's Huawei are set to overshadow the three-day pomp fest.
The president and his wife, First Lady Melania, began with a ceremonial welcome at Buckingham Palace.
But activists plan to rival the festivities with a "carnival of resistance" And the "Trump baby" blimp will also be back, flying over parliament.
In what is likely to be the most unconventional state visit in recent memory, Trump has already waded far into British domestic politics.
In an interview with the Sunday Times, he said Britain should refuse to pay its 50-billion-dollar divorce bill - Walk away from Brexit talks if Brussels won't give it what it wants - And that arch-Brexiteer Nigel Farage should be the one to conduct those talks.
Trump also weighed in on who Britain's next prime minister should be.
The hard Brexiteers got his vote - including former foreign minister Boris Johnson, who favors Britain leaving the EU in October with or without a deal.
Trump is also expected to use the trip to demand a tougher British stance on China and telecoms giant Huawei.
Before he set off for the UK, the president repeated his message that there was an opportunity for a "very big trade deal" between the two countries in the near future.
Britain prides itself on its so-called special relationship with the United States.
Theresa May was the first foreign leader to visit Trump after his inauguration.
But some Brits see the leader as volatile and hostile to their values on immigration and the treatment of women.