Watch: President Biden, first lady meet Queen Elizabeth II
Joe Biden has said the Queen reminded him of his mother after he had tea with her at Windsor Castle on Sunday afternoon.
Biden, 78, said he did not think the Queen, 95, would "be offended" before he made the remark, as he boarded the Marine One plane at Heathrow to head to Brussels.
He said she reminded him of his mother in the "look of her and her generosity".
He and his wife Jill Biden spent about an hour with the Queen in total, arriving at Windsor Castle just after 5pm, and leaving at 6.03pm.
They saw a Guard of Honour, which Biden inspected, before the Queen led them through the Sovereign's Entrance and served them tea.
As he was leaving the UK, Biden told waiting reporters about the visit: "We had a long talk. She was very generous. I don’t think she’d be insulted but she reminded me of my mother. In terms of the look of her and just the generosity."
He said he had invited her to the White House, and that he joked the presidential home and office could fit inside the Quadrangle of her Berkshire castle.
The Queen has not travelled abroad since 2015 when she went to Malta with her late husband Prince Philip.
Her son Prince Charles and his wife Camilla travelled to the US in 2015 on her behalf and met with Biden when he was Vice President.
White House reporter Jennifer Jacobs said Biden also remarked that the Queen had asked him about his upcoming visit with president Xi Jinping and president Vladimir Putin.
Biden added: "She said, ‘What’s it like in the White House?’ I said, ‘Well it’s magnificent but it’s a lot of people’."
Biden is continuing his trip, next heading to Brussels, but his wife Dr Biden is returning to the US.
The first lady spent time with the Queen's granddaughter-in-law, attending a school with her in Cornwall on Friday, where the pair met some of the pupils in reception class, before sitting on a round table about education and Early Years development.
The two women then released an op-ed through CNN, establishing their commitment to working together on Early Years Development.
When Dr Biden was quizzed on whether she asked the Duchess of Cambridge for advice on meeting the Queen, she brushed off the suggestion, saying they were "busy".
Biden is the 13th president the Queen has met during her reign, of 14 who have been in power across the pond.
They met briefly on Friday evening in Cornwall, the first time the Bidens had met the Queen despite his eight years as vice president when he worked with Barack Obama.
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