US President Donald Trump has said the relationship between the US and the UK is very strong, and that a "big" trade deal was possible once the UK "gets rid of the shackles".
Taking to twitter during his three-day state visit to the UK, Mr Trump said the trip was going "really well".
"London part of trip is going really well. The Queen and the entire royal family have been fantastic. The relationship with the United Kingdom is very strong. Tremendous crowds of well wishers and people that love our country," he said.
He also added that a "big trade deal is possible once the UK gets rid of the shackles".
Mr Trump earlier met Queen Elizabeth at Buckingham Palace, having begun his visit by calling London Mayor Sadiq Khan a "stone cold loser" for criticising the decision to roll out the red carpet for him.
With a 41-gun royal salute ringing out across the royal palace's front lawn, Mr Trump shook hands with the queen before stepping inside for a lunch reception.
He and his wife Melania were met on arrival at the palace by Prince Charles and his wife Camilla.
While Mr Trump has visited the UK before, this is his first official state visit involving far more ceremonial and royal events.
Mr Trump has arrived back at Buckingham Palace in Marine One for a state banquet, where both he and the Queen will make speeches.
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Tomorrow, Mr Trump will hold talks with British Prime Minister Theresa May just days before she formally steps down as leader of the Conservative Party.
However, they will not have formal one-to-one discussions during the visit.
The two leaders will be joined by their delegations of senior officials and ministers for a bilateral meeting.
Downing Street insisted it was normal for meetings between the two leaders to take place with their delegations.
Mrs May's spokesman said she will discuss future economic ties with the president, adding that both have repeatedly expressed a shared desire for a trade deal after Brexit.
Speaking to reporters just before he left the US, he praised Boris Johnson and Nigel Farage, talked up the prospect of a Brexit trade deal, and rebuked Mr Khan.
As he landed he mis-spelled the London Mayor's name and mentioned his height, writing: "@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......
"...Kahn reminds me very much of our very dumb and incompetent Mayor of NYC, de Blasio, who has also done a terrible job - only half his height. In any event, I look forward to being a great friend to the United Kingdom, and am looking very much forward to my visit. Landing now."
.@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......
— Donald J. Trump (@realDonaldTrump) June 3, 2019
In return the mayor's office said Mr Trump was offering "childish insults which should be beneath the President of the United States".
The US President and Mr Khan have repeatedly clashed in recent years, including Mr Trump criticising the mayor's response to the 2017 London Bridge terror attack.
A spokesman for Mr Khan said: "Sadiq is representing the progressive values of London and our country warning that Donald Trump is the most egregious example of a growing far-right threat around the globe, which is putting at risk the basic values that have defined our liberal democracies for more than 70 years."
Major protests are expected against Mr Trump's visit, particularly tomorrow when a number of demonstrations are planned for central London.
On Wednesday, he will attend commemorations marking the 75th anniversary of D-Day before leaving Britain to travel to Ireland.
Speaking to reporters over the din of his waiting Marine One helicopter last night, Mr Trump was asked if he planned to meet Mr Johnson during the trip.
"Well, I think I may meet with him. He's been a friend of mine. He's been very nice. I have a very good relationship with him," the president said of the Tory leadership hopeful.
He went on: "I have a very good relationship with Nigel Farage, with many people over there (in the UK) and we'll see what happens. I may meet with him. They want to meet. We'll see what happens."
Accompanied by first lady Melania Trump, the president departed from Joint Base Andrews near Washington DC aboard Air Force One, and arrived at Stansted Airport this morning.
Mr and Mrs Trump stepped off Air Force One amid windy conditions and were greeted by US Ambassador to the UK Woody Johnson and Foreign Secretary Jeremy Hunt.
They then headed to Winfield House, the ambassador's residence in London, before being flown by helicopter to Buckingham Palace.
