In a tweet insulting London's Mayor Sadiq Khan, the president said "Kahn reminds me very much of our very dumb and incompetent Mayor of NYC, [Bill] de Blasio who has also done a terrible job".

He then says Khan is "only half his height".

Press Association's chief political photographer tweeted this image of the pair in response.

Image source, PA

If you want a chance to glimpse the US President in the flesh today, your best bet may be to join the crowds on The Mall in central London.

The next item on today's jampacked agenda involves Mr Trump attending a ceremonial welcome to meet the Queen, Prince of Wales and Duchess of Cornwall in the Buckingham Palace garden.

After the welcome, the Duke of Sussex will join the group for a private lunch at the palace.

Image source, Reuters

Image source, Reuters

The Duchess of Sussex will not attend - which means she'll avoid an awkward conversation about whether or not the president said she was "nasty".

Mr Trump will also have tea with Prince Charles and the Duchess of Cornwall at Clarence House, which is just off The Mall.

Tonight, the Queen will host a state banquet at the palace for the president and the First Lady Melania Trump.

Political scientist and author Brian Klass says President Donald Trump is doing "immense damage" to the US' "most important alliances".

Liberal Democrat leader, Vince Cable, says Donald Trump was invited to the UK to "deal with the Brexit problem".

Daniel Mcilhiney, from Trump UK, a campaign group which supports the president, said referring to Donald Trump as a fascist sets a "dangerous" precedent.

It comes after Sadiq Khan told the Observer, external ahead of the state visit that the president is "just one of the most egregious examples of a growing global threat".

Mr Khan then went on to compare Mr Trump to Marine Le Pen in France and Nigel Farage, accusing them of "using the same divisive tropes of the fascists of the 20th century to garner support, but with new, sinister methods to deliver their message".

Mr Trump hit back at Mr Khan this morning, calling him a "loser" in a series of critical tweets.

But despite this, Mr Mcilhiney said "we have to show respect for his office".

Mr Mcilhiney said: "I don’t think it's fair to lay all the blame at Trump's door.

"We are entering into political and economical turmoil at the moment and we need trade deals, we need to start making friends, we can't start cutting off our nose to spite our face because we don’t like the fact he called our mayor a loser."

Image source, Getty Images

Protesters have unfurled five 20m-long banners opposite the US Embassy to "resist" the US president's "trashing of human rights".

Amnesty International's banners on Vauxhall Bridge say “Resist sexism”, “Resist racism”, “Resist hate”, “Resist cruelty” and “Resist Trump”.

Kate Allen, the charity's UK section director, said: “Trump has presided over two-and-a-half years of utterly shameful policies.

“Locking up child migrants, imposing a discriminatory travel ban, decimating global funding for women’s rights and withdrawing from global human rights bodies... We need to resist Trump’s trashing of human rights."

The Amnesty stunt is the first of several protests expected during Mr Trump's three-day visit.

The Foreign Secretary says he is "hugely excited" about the days ahead.

A survey by the University of Oxford has analysed over 8,000 of President Trump's tweets since he was elected in 2016, and found that the UK came in 15th place of the most-referenced countries.

In the top spot is Russia with 297 out of 1,384 mentions. Other favourites were North Korea (163), China (158), Mexico (99), Puerto Rico (47) and Iran (47).

Image source, Getty Images

The president has brought a fleet of helicopters with him, which he's put into use straight away to make the journey from Stansted Airport to the US Ambassador's residence in Regent's Park.

Among the fleet is Marine One, which, like Air Force One, isn't a specific aircraft but instead refers to any US Marine Corps aircraft carrying the president.

The specially-adapted helicopters are known as "white tops" because of their livery and are fitted with communications equipment, anti-missile defences and hardened hulls.

As a security measure, Marine One often flies in a group of identical helicopters acting as decoys.

It is also usually accompanied by two or three Osprey MV-22 escort aircraft,, external referred to as "green tops".

These tilt-rotor aircraft carry support staff, special forces and secret service agents, who are tasked with dealing with any mid-flight emergency.

Read more about what Mr Trump has brought with him here.

Image source, Reuters

The Museum of London says it wants the Donald Trump baby balloon as an exhibit.

The blimp was flown over Parliament Square during the US President's working visit to the UK in July 2018.

Campaigners raised almost £18,000 to pay for the 6m-high (19.7ft) inflatable and London Mayor Sadiq Khan gave permission for it to fly.

The museum said the owners of the balloon were keen for it to go on display there.

Museum of London director Sharon Ament said it would also like to display a balloon depicting Mr Khan in a yellow bikini.

Read more here

Image source, EPA

After touching down at Stansted Airport, the presidential convoy has made its way to Winfield House in Regent's Park.

It's an almost 50-mile journey - but no need to queue in rush-hour traffic when you're the US President.

Mr Trump has made the short journey to the US Ambassador's residence by helicopter.

The picture below shows the security team at Winfield House making preparations yesterday.

Image source, PA

A spokesman for the Mayor of London Sadiq Khan responded to tweets sent by President Trump, in which he called Mr Khan a "stone cold loser".

The 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, 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."

US President Donald Trump and First Lady Melania Trump have arrived in the UK for a three-day state visit.

The Presidential plane Air Force One landed at Stansted Airport in Essex shortly before 09:00 BST.

Asked about what he thought of President Trump's tweets about Sadiq Khan, Foreign Secretary Jeremy Hunt said: "I actually agree with him that it's totally inappropriate for the Labour Party to be boycotting this incredibly important visit. This is the President of the United States."

Mr Hunt added that the visit and what it represents should be "above party politics".

President Donald Trump will visit the Queen during his trip to the UK - marking the latest in a long history of meetings between the British monarch and US heads of state.

In her 66-year reign, Queen Elizabeth II has met nearly all of the 12 presidents in office during that time.

Image source, Getty Images

Image source, Getty Images

Image source, Getty Images

Read more here

Image source, PA

Buckingham Palace is where much of the pomp and ceremony of the first day of the presidential visit will take place - so, naturally, members of the world's media have descended there this morning.

Both Mr Trump and the Queen are expected to make a speech to guests - which will include prominent Americans living in Britain - during a state banquet at the palace later.