A new photograph has been released to mark the occasion which shows the Queen and Prince Philip sitting together on a sofa in the Castle’s Oak Room. The royal couple can be seen opening and reading handmade anniversary cards their great-grandchildren Prince George, Princess Charlotte, and Prince Louis.
The gift from George, Charlotte and Louis features a large number 73 which has been coloured in with stripes and pops out from the front of the card.
On a nearby table, there is also a small pile of anniversary cards and letters sent by well-wishers.
The photo, taken by Chris Jackson from Getty Images, joins a collection of thousands of pictures taken over the decades documenting the history of their enduring relationship.
The Queen was a 21-year-old princess when she married Lieutenant Philip Mountbatten at Westminster Abbey on 20 November 1947. They have been married longer than any British sovereign and consort.
The monarch can be seen wearing a Chrysanthemum Brooch, the same brooch that she was wearing during her honeymoon.
She was also seen wearing it in photographs taken to mark their 60th wedding anniversary in 2007.
The Queen and Duke, who has retired from public duties, are spending the second coronavirus lockdown in England isolating together at Windsor Castle.