He arrived in Air Force One at Stansted Airport yesterday morning and had a jam-packed day culminating in a banquet at Buckingham Palace.
But before the feast was served up, the Queen gave a speech to mark the occasion - during which the US President appeared to take the opportunity to catch some micro-sleep.
While Her Majesty highlighted 'the common values and shared interests' that unite the UK and the US, Trump appeared to indulge in a series of long blinks, followed by a few seconds of 'eye resting'. He then flashed open his eyes suddenly, as one does when they realise they've accidentally nodded off on the bus.
The Queen then made a toast and Trump no doubt hoped nobody (except him) had even batted an eyelid. But of course, in this day and age, you can let your guard down for just a few seconds and it's all over social media in the blink of an eye.
Donald Trump appeared to have a little micro-sleep during the Queen's speech. Credit: PA
Taking to Twitter, one person said: "Good, god, he's falling asleep at the royal dinner."
Another said: "He falls asleep at one point in this. What an embarrassment."
A third tweeted Mr Trump directly and said: "You fell asleep during THE QUEEN'S speech! You are a total embarrassment to our country and the world."
On the face of it, drifting off during the Queen's speech doesn't have a great ring to it, but the 72-year-old had a big old day that would take it out of most of us.
Plus, he may not have even fallen asleep at all. Certainly, if you ask him, he will almost definitely deny enjoying a few seconds of sleepy time.
The Queen and Trump shared a chuckle during the banquet. Credit: PA
So yeah, given his track-record, don't be surprised if this apparent micro-sleep is chalked off as a moment of inward reflection or something.
Trump is due to have talks with Prime Minister Theresa May today (Tuesday) at 10 Downing Street, where they are expected to discuss issues such as climate change.
Meanwhile, Labour leader Jeremy Corbyn will be speaking at a protest rally in London.
Featured Image Credit: Associated Press