It is “exceptionally rare” for anyone, including the UK Prime Minister, to reveal to the public the contents of the meeting with the 95-year-old monarch.
On Sunday evening, at the Heathrow airport moments before leaving for Brussels, Mr Biden told the media: “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.”
The Queen also quizzed the US president about Xi Jinping and Vladimir Putin. He told reporters: “She wanted to know what the two leaders that I — the one I’m about to meet with, Mr Putin, and she wanted to know about Xi Jinping.”
Mr Biden is meeting with his Russian counterpart next week as he continues with his European tour.
He was accompanied by the US First Lady Jill Biden at Windsor Castle.
Mr Biden had earlier mentioned that the relations of the two countries — the US and Russia — were at a historically low point. “I think the best way to deal with this is for him and I to meet.”
Speaking to White House correspondents about his meeting with the Queen, Mr Biden said: “I said I wish we could stay longer, maybe we could hold the cars up a minute, and stuff. Anyway, she was very gracious.”
The Queen also introduced the US President and the First Lady to her lady-in-waiting Dame Annabel Whitehead before stepping inside.
Mr Biden said he has extended an invitation to the Queen to visit the White House.
In 2012, a BBC security correspondent, Frank Gardner, was forced to apologise publicly after he revealed on Radio 4 what the Queen had told him about Abu Hamza, the imam of Finsbury Park mosque in north London.
Press Association had earlier also reported a snippet of the conversation between the Queen and Mr Biden. It reported that the Queen said to the president: “You completed your talks,” to which Mr Biden replied: “Yes we did.”
Arriving in a black Range Rover after flying on the Marine One presidential helicopter, Mr Biden was greeted by the Queen who was standing alone, two months after the death of her husband, Prince Philip.
The royal family has taken an active role during the G7 summit, with the Queen hosting a reception for Biden and other G7 leaders at the Eden Project in Cornwall, also attended by Prince Charles and his wife Camilla, the Duchess of Cornwall, and Prince William and his wife, Kate, the Duchess of Cambridge.
The Queen received the Trumps in 2018, the Obamas in 2016, President George W Bush and his wife in 2008 and the Reagans in 1982.
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