Britain's Queen Elizabeth II waits for the arrival of US President Joe Biden at Windsor Castle near London, Sunday, June 13, 2021. (AP Photo/Alberto Pezzali)

Britain's Queen Elizabeth II arrives to meet with US President Joe Biden before receiving a Guard of Honour at Windsor Castle near London, Sunday, June 13, 2021. (AP Photo/Alberto Pezzali)

Britain's Queen Elizabeth II is seen during a visit by US President Joe Biden (not pictured) at Windsor Castle in Windsor, west of London, on June 13, 2021. - US president Biden will visit Windsor Castle late Sunday, where he and First Lady Jill Biden will take tea with the queen. (Photo by Chris Jackson / POOL / AFP)