The Royal Family had many memorable interactions with President Obama and First Lady Michelle Obama over the years.
Whether it is them taking part in a funny skit with the Queen and Prince Harry for the Invictus Games, or reports about Prince Philip scaring the couple's bodyguards when he insisted on driving them back to Windsor Castle himself, there are several to choose from.
But one of the most famous moments came in 2016 during the Obamas final visit to the UK before the President left office, as he met the-then two-year-old Prince George in his dressing gown at Kensington Palace.
Shortly after the Presidential couple were pictured with the-then Duke and Duchess of Cambridge and Prince Harry outside the West London palace, they went inside where there was another special guest waiting to meet them.
The Kensington Palace social media accounts quickly released images of Prince George in his pyjamas and dressing gown shaking hands with the outgoing President.
In a separate image, the young royal, who had been allowed to stay up past his bed time, was seen sitting on a wooden rocking horse that had been gifted to him by the couple when he was born in 2013.
The handmade rocking horse comes with a polo mallet, and the presidential seal emblazoned on the saddle.
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Mr Obama later described George as "adorable" during the trip and joked that the young royal's attire showed how people started to change as he prepared to leave his position.
He laughed that George's wardrobe was similar to how his political opponents were no longer answering his phone calls.
The President quipped: "It's not just Congress. Even some foreign leaders they have been looking ahead, anticipating my departure. Last week Prince George showed up to our meeting in his bath robe. That was a slap in the face. A clear breach of protocol."
Another special moment between the Royal Family and the Obamas was seen during their first state visit to Buckingham Palace in 2009.
While standing next to each other at a small reception, Michelle opted to put her arm around the monarch.
To everyone's astonishment, the Queen reciprocated the gesture and placed her gloved hand on the former First Lady's back. Protocol dictates that you should refrain from touching the royals, unless they initiate the contact.
In 2018, Michelle spoke about why she put her arm around the Queen and what happened afterwards in her best-selling memoir, Becoming.
She said: "The Queen glanced down at the pair of black Jimmy Choos I was wearing. She shook her head. 'These shoes are unpleasant, are they not?'
"She gestured with some frustration at her own black pumps. I confessed then to the Queen that my feet were hurting. She confessed that hers hurt, too.
"We looked at each other then with identical expressions, like, when is all this standing around with world leaders going to finally wrap up? And with this, she busted out with a fully charming laugh."
