It's been a week of 90th birthday celebrations for the Queen, and Friday was no different. Her Majesty welcomed guests of honour the President of the US Barack Obama and First Lady Michelle for a special post-birthday luncheon – and Prince Philip was on hand to act as chauffeur.
The royals threw open the doors of Windsor Castle to welcome their American guests, who touched down in the grounds of the Berkshire estate via helicopter, alongside their entourage.
The Obamas are on a three-day visit to the UK and tonight will meet Prince William, Prince Harry and William's wife Kate for dinner.
The group enjoyed a lavish lunch at Windsor Castle
Dressed in pale blue, the Queen welcomed Barack and Michelle to her countryside home. The Prince, 94, then drove the group back to the castle.
First Lady Michelle was on top sartorial form, wearing a bright pink and purple patterned dress and matching purple coat.
Barack and Michelle presented the Queen with a personalised photo album of her visits with US Presidents and First Ladies through the years.
Prince Philip, 94, drove the Queen and his guests back to Windsor Castle
The royals and the Obamas have met several times during the American leader's presidency and they enjoy a warm personal relationship. In 2009 Michelle famously broke royal protocol and put her arm around the Queen during a reception at Buckingham Palace – only to have the monarch return the gesture and hug her back.
It was also then that the Queen spoke of her "fond memories" of first meeting the Obamas. Barack, for his part, paid tribute to the royal's "lifetime of extraordinary service to her nation and to the world" and thanked her for the "warm friendship" she had extended.
Barack, 54, and the 90-year-old monarch were last pictured together in June 2014 at the 70th anniversary for D-Day. The pair were joined by other leaders and dignitaries at Normandy, including the Queen's relative Queen Margrethe II of Denmark.
The royals and the Obamas enjoy a warm personal relationship
This is most likely Barack's final official trip to the UK as president of the United States. A White House spokesman said: "The visit will allow the President to offer his gratitude to the British government and people for their stalwart partnership with his administration and the American people throughout his presidency."
Barack is also scheduled to hold a press conference with Prime Minister David Cameron on Friday.