Barack Obama and the First Lady have given the Queen a 90th birthday present - a reminder of her many visits to America.
The Queen was presented with a photo album chronicling her official engagements with US leaders and their wives.
Britain's head of state has made numerous trips across the Atlantic, from her first in 1951 when she was still Princess Elizabeth, which saw her tour George Washington's historic Mount Vernon estate and meet President Harry S Truman.
She also paid her respects at Ground Zero in New York in 2010, the site of the 9/11 terrorist attacks.
The Obamas have a warm relationship with the Queen and her family and were invited to have lunch with the monarch and the Duke of Edinburgh at Windsor Castle.
Philip showed the US leader and his wife the personal touch when he drove them and the Queen to Windsor Castle after the Marine One presidential helicopter had landed close to the monarch's Berkshire home.
The private lunch lasted around an hour before the Queen and Philip said goodbye to their guests.
Speaking at the Foreign and Commonwealth Office alongside David Cameron later in the evening, Obama paid a glowing tribute to the Queen, describing her as "a real jewel".
He said: "She's an astonishing person and a real jewel to the world, not just to the United Kingdom."
The President spoke fondly of their lunch together, and added: "As for her Majesty, the Queen has been a source of inspiration like so many people around the world.
"She is truly one of my favourite people, and should we be as fortunate to reach 90, may we be as vibrant as she is."