The 96-year-old monarch’s public appearances are being closely watched as Britain prepares to celebrate her 70 years on the throne next month.
“And where did you come from? I know what you want,” the queen chirped as her dog Candy -- a cross between a dachshund and a corgi -- trotted over to her desk.
On Christmas Day, police arrested a 19-year-old man who allegedly was in possession of a crossbow at the castle
Police responded within minutes after the intruder was spotted.
The queen made her first scheduled appearance since last week's overnight hospital stay.
Biden, who is in the U.K. for the Group of Seven leaders summit, is the 13th American president to meet the monarch.
Sophie, the Countess of Wessex, took the picture in the Scottish Highlands in 2003.
Buckingham Palace said the prince’s hearse was built when Philip turned 82, and modified over the years with an open-top rear section to hold his coffin.
The 94-year-old monarch decided to announce that she had gotten the jab.
Prince William accompanied his grandmother for the rare joint appearance.