Theresa May has become the first head of government to sign the White House guest book under US President Donald Trump.
White House press secretary Sean Spicer posted an image of the historic event on his official Twitter page.
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Donald Trump and Theresa May spoke of their pleasure at having a bust of Sir Winston Churchill moved back into the Oval Office.
Posing for cameras, the pair shook hands in front of the bust of Britain's World War II leader - removed from the office by Barack Obama.
The President quipped: "We'll see one picture tomorrow in the papers."
Referring to the bust, brought back by Mr Trump, the President said: "This is the original, folks. The original, in many ways.
"It's a great honour to have Winston Churchill back."
Mrs May laughed and responded that she was "very pleased."
President Donald Trump is on the verge of signing an executive order to temporarily halt refugees from some countries, according to a White House official.
The plan would involve refugees being denied visas from several Muslim-majority nations.
Mr Trump is expected to sign further executive orders relating to military readiness and national security on a visit to the Pentagon later on Friday, the official added.
Theresa May has arrived at the White House for her meeting with Donald Trump.
The President met the Prime Minister as she exited her car, and escorted Mrs May into his official residence.
Theresa May will be looking for guarantees from Donald Trump that American won't "stand idly by" in the face of Russian aggression.
ITV News Political Editor Robert Peston believes the Prime Minister hopes the US President will his signal support for NATO - rather than an intention to loosen sanctions against Russia.
Mr Trump has previously described NATO as "obsolete," and suggested he might be willing to drop sanctions imposed by Barack Obama.
Peston, who is in Washington, said of the upcoming meeting between Mrs May and Mr Trump: "She wants him to basically say he stands by the principle of NATO: That an attack on one member is an attack on all.
"This is particularly important when we see the confidence of Vladimir Putin, and his very clear aims of exerting greater influence over the countries of the former Soviet Union."
He added that there were "tremendous fears" in Baltic States about a future Russian invasion.
Russia's UK embassy criticised a speech by Theresa May about Vladimir Putin - through rhyming poetry.
The embassy chided the Prime Minister after she called on US President Donald Trump to "beware of" the Russian leader.
In a speech delivered on Thursday, Mrs May urged Mr Trump to engage with the Kremlin "from a position of strength."
Her comments appeared to have irked the London-based Russian embassy, who tweeted their response in the form of ABAB poetry.
Russian Embassy, UK, wrote that they believed the Cold War to be "long dead."
Prime Minister Theresa May has laid a wreath in Arlington Cemetery to pay her respects to the US military dead.
Dressed in sombre black, the PM was greeted by troops representing all military units based in Washington, led by Major General Bradley Becker, commander of Joint Force Headquarters for the national capital region.
The Tomb of the Unknowns at the Virginia cemetery holds the remains of unidentified US troops from the First and Second World Wars, as well as the Korean conflict.
More than 400,000 US troops killed in conflicts from the Civil War to the ongoing War on Terror are laid to rest at Arlington.
Among them are a number of British troops who died fighting alongside US forces.
She will meet with US President Donald Trump at the White House at 5pm (UK time).
The PM, the first foreign leader to hold talks with the President, is expected to have UK-US trade post-Brexit at the top of the agenda.Read the full story ›
The former Labour leader also said he was sceptical of an early trade deal with the US which he said could be a "dangerous Trojan horse".Read the full story ›