The two leaders inked a major deal on tech investment that officials say will bring thousands of jobs and billions in investment in artificial intelligence, quantum computing and nuclear energy.
They are also expected to discuss steel tariffs and potentially tricky topics including the wars in Ukraine and Gaza.
On Wednesday, the president and first lady Melania Trump were feted by King Charles III and Queen Camilla at Windsor Castle with gold-trimmed carriages, scarlet-clad soldiers, artillery salutes and a lavish banquet in a grand hall.
No U.S. president, or any other world leader, has ever had the honor of a second U.K. state visit.
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The president claimed not to know former British Ambassador to the U.S. Peter Mandelson, but the photographic evidence says otherwise.
Mandelson lost his job due to ties to Jeffrey Epstein, the deceased investor tied to sex trafficking who also had a relationship with Trump.
When asked about Mandelson, Trump said, "I don't know him actually."
But Mandelson was standing right next to a seated Trump in the Oval Office on May 8 when the two countries announced a trade framework.
"And he said a horrible thing about a great gentleman known as Charlie Kirk," Trump said.
The president was asked if free speech is more under attack in Britain or the United States. He repeated his view that Kimmel isn't talented. Kimmel has sharply criticized Trump and Trump's administration in many of his routines.
"He had very bad ratings, and they should have fired him a long time ago," Trump said. "So, you know, you could call that free speech or not. He was fired for lack of talent."
The president said at a news conference said that the U.S. was getting a "fee plus" for brokering the sale of TikTok assets to an American buyer, adding that he personally uses the social media video app "very legitimately."
The China-associated app has raised national security concerns, prompting a law requiring its owner ByteDance to sell TikTok's U.S. operations or have the app banned. Trump has extended the ban deadline multiple times since January. Trump is slated to speak Friday with Chinese leader Xi Jinping.
Trump said that the assassinated conservative activist Charlie Kirk first encouraged him to get on TikTok.
"The United States is getting a tremendous fee plus," said Trump, not defining what that term meant relative to the framework for a deal.
Starmer says the timing of Britain recognizing a Palestinian state — expected within days — has nothing to do with the state visit.
It came after reports that Starmer was waiting for the trip to be over before making the move.
Starmer has defended Britain's record on free speech, which has been criticized by allies of President Trump.
He was asked about people being arrested for posts on social media. The U.K. has laws that seek to limit online hate speech and try to stop children seeing suicide sites and other harmful content.
Starmer said the U.K. is proud of its centuries-old tradition of free speech. He said "I am all for free speech. I am also for protecting children from things that will harm them."
"We're trying to get it back," Trump said in an aside as he lamented the difficulty of solving wars that weaved into him slamming President Joe Biden for how he carried out the U.S. withdrawal from Afghanistan.
Trump described his call for the U.S. military to re-establish a beachhead in Afghanistan as "breaking news" but he has previously raised the idea.
The president repeated his view that a U.S. presence at Bagram is of value because of it's proximity to China, the United States most significant economic and military competitor.
A judge is blocking the Trump administration from immediately deporting Guatemalan migrant children who came to the U.S. alone back to their home country.
The Thursday decision by U.S. District Judge Timothy J. Kelly comes after the Republican administration's Labor Day weekend attempt to remove Guatemalan migrant children who were living in government shelters and foster care.