The 94-year-old Queen attended a series of exercises by the 1st Battalion of the Welsh Guards in the castle quadrangle, instead of the traditionally popular Trooping the Colour event.
The Queen, who has lived with her 99-year-old husband Prince Philip at the castle in west London, has posted a number of rallying messages to the nation over the past three months, including televised speeches that have been a rarity during her 68-year reign.
But she had only been seen in public on Saturday, wearing a jade coat and wearing a diamond Welsh Guards brooch, watching soldiers adhere to the 2-metre social distance rule and listening to music performed by a band from the household division.
Earlier this week, Buckingham Palace released a new photo of the royal couple to celebrate Philip’s birthday. The pistol salutes in London that normally celebrate this occasion have also been cancelled.
The Queen’s real birthday is April 21, but her birthday is officially marked in June.
Reporting by Sarah Young; Editing by Frances Kerry
Our standards:The principles of the Thomson Reuters Trust.