WINDSOR: Normally the US Secret Service is pretty strict about President Barack Obama getting into non-armoured cars with non-expert drivers, but on Friday they made an exception.
On Obama's arrival at Windsor Castle, the president and First Lady Michelle Obama -- code names "Renegade" and "Renaissance" -- were picked up from their Marine One helicopter by Queen Elizabeth II and her 94-year-old husband Prince Philip, who was in the driver's seat.
Obama and the prince, formally known as the Duke of Edinburgh, got in the front of the Range Rover and the queen and First Lady sat in the back.
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This is Obama's fifth trip to Britain as president, and aides say he has enjoyed meeting the country's longest-serving monarch, who has greeted US presidents since Harry Truman.
The two couples had lunch together at Windsor, the queen's weekend residence located west of London, to mark her 90th birthday, which was on Thursday.
But the trip also marks what is likely to be Obama's last presidential visit to Britain and meeting with the queen.
As a gift, the White House said the Obamas presented the queen "with a custom photo album chronicling her visits with US presidents and first ladies".
"The collection of historical photos in the album highlights the enduring close friendship between the United States and the United Kingdom," the White House said.
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The queen's first visit to the United States was in 1951m before the start of her long reign.
The only president since Truman that she has not met was Lyndon B. Johnson.