In the photo, the Queen is pictured wearing a pale blue double wool crepe dress by Stewart Parvin and a chrysanthemum brooch made from sapphires and diamonds set in platinum, while Philip, who is holding the card, looks smart in a navy blazer, shirt and tie, and grey trousers.
The Queen and Prince Philip got married at London's Westminster Abbey on 20 November 1947, just two years after the end of the Second World War, in a ceremony which attracted statesmen and royalty from around the world and huge crowds of well-wishers who lined the streets.
The couple met when they were very young, with the Queen once writing a letter about the time she met Prince Philip, then Philip Mountbatten. She wrote that the two of them first met at the Royal Naval College in July 1939, when she was just 13-years-old, admitting that she quickly fell for the 18-year-old naval cadet.
Their engagement did not come for another eight years, after the war, in 1947, with the marriage taking place just four months later. Within a matter of five years, Elizabeth ascended to the throne and took her vows as Queen Elizabeth II, after her father, King George VI, died of coronary thrombosis aged 56.
After her first two children, Queen Elizabeth II waited more than a decade before having another. She and Prince Philip welcomed their third child, Prince Andrew, in 1960, and their youngest, Prince Edward, in 1964.
In March, the couple moved out of Buckingham Palace to live in Windsor due to the coronavirus pandemic.
At the time, a statement on the royal family’s official Twitter account said that a “number of changes” were being made to the monarch’s schedule “as a sensible precaution and for practical reasons in the current circumstances”.
In August, the royal couple travelled to Scotland for their annual summer break at Balmoral, before moving to Sandringham, where they resided for several weeks.
However, on Tuesday 6 October, they returned to the royal residence in Windsor.