The last public picture of the Queen was taken as she was driven away from Buckingham Palace to her Windsor Castle home on March 19.
One of the Queen's corgis - she has two named Candy and Vulcan - could be seen next to her as they both looked out of the car window.
The Queen carried out official duties the day before her planned departure, but held her weekly audience with Prime Minister Boris Johnson on the phone rather than face to face as usual.
The Queen has made two televised addresses to the nation during the lockdown, the first a speech to reassure the country that coronavirus would be overcome and those in isolation "will meet again", and another on a similar theme to mark VE Day.
She has been joined by the Duke of Edinburgh at Windsor Castle and it is likely a small group of household staff have been isolating with her.