More than 170 ambassadors and high commissioners are based in London, each of whom receives an audience from the Queen shortly after starting their job.
This is the first time the Queen has been photographed carrying out her duties since Philip died on April 9, though behind the scenes, she was back at work four days after his death.
On April 13, she held a ceremony to mark the retirement of her former Lord Chamberlain, Earl Peel, and invested him with the Royal Victorian Chain.
The Lord Chamberlain is the most senior official in the royal household. Earl Peel was replaced by Baron Andrew Parker.
On April 17, the Queen cut a lonely figure as she said her final goodbye to Philip, her husband of 73 years.
The Duke of Edinburgh's funeral in St George's Chapel was held in accordance with coronavirus restrictions, meaning only 30 family members and close friends were allowed to attend.
Her Majesty sat alone in the choir, while other mourners were separated into family bubbles. She spent much of the service with her head bowed in silence.
In a message to mark her 95th birthday on April 21, the Queen thanked the public for their support during a time of "great sadness" for the family.
"While as a family we are in a period of great sadness, it has been a comfort to all of us to see and to hear the tributes paid to my husband, from those within the United Kingdom, the Commonwealth and around the world," she said.
"My family and I would like to thank you for all the support and kindness shown to us in recent days. We have been deeply touched and continue to be reminded that Philip had such an extraordinary impact on countless people throughout his life."
