The Queen enjoyed a joke with US President Barack Obama as she welcomed him to Buckingham Palace for a much anticipated first meeting.
The historic encounter between the monarch and the American leader happened ahead of a reception at the palace for the G20 politicians and heads of world organisations.
The Queen, 82, and Mr Obama, 47, were joined by their spouses the Duke of Edinburgh, 87, and Michelle Obama, 45, for private talks.
Mr Obama and wife Michelle arrived at the palace in their chauffeur-driven car - known as The Beast - and looked relaxed as they were greeted on the steps of the Garden Entrance by the Master of the Household Air Vice-Marshal David Walker.
Meeting her visitors inside the palace, the Queen smiled warmly as she shook hands with Mrs Obama while their husbands looked on.
The foursome chatted briefly in front of photographers, who were allowed to record the initial moments of the meeting. Mr Obama told the Queen: "Thank you so much for having us."
Addressing the Duke, he said: "It's a wonderful honour."
A Palace spokesman said the Obamas presented the Queen with a personalised iPod containing a video of her visit to Virginia, Washington, in 2007.
In return, the royal couple gave them a silver-framed, signed photograph of themselves.
