Four people have been arrested on suspicion of malicious communications following a "public stunt in Windsor".
Several images and clips of Donald Trump and Jeffrey Epstein were projected by protesters onto Windsor Castle as the President landed in the UK for his state visit.
Thames Valley Police said they are being held in custody.
Meanwhile, a separate incident saw two protesters from the activist group Fossil Free London escorted out of a dinner in Windsor - though they were not arrested.
Protesters projected images of Donald Trump and Jeffrey Epstein onto Windsor Castle
|GB NEWS
The man and woman entered the dinner, which had been organised by Republicans Overseas UK, chanting "how many will you kill if you drill baby drill".
The pair also unfurled a banner which read: "Oily Money Kills."
Greg Swenson, the chairman of Republicans Overseas UK, later revealed to GB News what happened inside.
"They snuck in as people were settling in. It was actually brilliant," he said. "They had to be dragged out - which is their thing. It was actually entertaining."
Diners eventually managed to wrangle the flag away from the protesters - with Mr Swenson jabbing: "We captured the flag!"
Attendees of the dinner had previously held a moment of silence for Donald Trump ally Charlie Kirk who was assassinated last week.
Mr Swenson said: "[Mr Kirk] was persuasive. He persuaded. He made the argument.
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Diners at the Republicans Overseas UK event eventually managed to wrangle the flag away from the protesters
|GREGG SWENSON
Four people have been arrested over the incident
| GB NEWS"He wasn't mean about it, like these idiots who interrupted our private function, but it's testament to you all in this room, and I'm thrilled that you're here."
A spokesman for Thames Valley Police said: "We received a report of a public order incident at a private event in Windsor Guildhall at approximately 8.45pm this evening [September 16].
"Two individuals were removed by the event organisers and no arrests were made."
Responding to the four arrests, Chief Superintendent Felicity Parker said: "We take any unauthorised activity around Windsor Castle extremely seriously.
President Trump's relationship with Epstein has dominated US politics recently
| GB NEWS"Our officers responded swiftly to stop the projection and four people have been arrested.
"We are conducting a thorough investigation with our partners into the circumstances surrounding this incident and will provide further updates when we are in a position to do so."
The President's relationship with the convicted paedophile has dominated US politics recently as critics called for all of the Epstein files to be released - as Mr Trump promised during his 2024 presidential campaign.
The two were both socially and professionally involved from the late 1980s to the early 2000s.
WATCH: Donald Trump speaks to the press as he arrives in Britain for his State Visit
Mr Trump denies any knowledge of Epstein's criminal activities.
The President arrived in the UK alongside his wife Melania on Tuesday for a three-day State Visit.
The pair landed at London Stansted Airport on Air Force One before heading to the American ambassador's residence in central London, where Mr Trump spoke with reporters.
The President said Wednesday "is going to be a very big day" and discussed his plans to meet with his "long time" friend King Charles.
PICTURED: An anti-Trump protest which took place in London in 2019. The President is set to face further demonstrations during his State Visit this week
|GETTY
Thousands of people are expected to turn out in London on Wednesday to participate in more anti-Trump protests.
A march organised by the Stop Trump Coalition is set to include speeches from Zack Polanski, the new Green Party leader, and disgraced ex-Labour leader Jeremy Corbyn.
Protests in the streets of the capital took place during the President's visit in 2018, with organisers claiming a turnout of 250,000.
However, these numbers were not verified.
During his last state visit in 2019, anti-Trump protests rocked the city - with then-Labour leader Mr Corbyn and then-Shadow Home Secretary Diane Abbott among those who spoke at the event.
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