Appearing in a vibrant green suit with matching hat, the 96-year-old monarch looked radiant as she smiled and waved at the crowds.
Well-wishers packing the mall burst into the national anthem, as did the members of Queen's family who surrounded her, including the Duke and Duchess of Cambridge and their three children, Prince George, Princess Charlotte and Prince Louis.
There was another special family connection during the Queen's three-minute appearance that was a little more subtle, however: her choice of brooch.
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The Queen is known to be a big fan of brooches and is thought to have a collection of more than a hundred, all of which have special meaning.
The diamond bow brooch that she chose to wear on Sunday is especially meaningful, as it carries a long family history and is one of a trio in different sizes with the same design that the Queen has worn on poignant royal occasions.
The Queen beamed as she was cheered by well wishers
The monarch's great-great-grandmother Queen Victoria often wore the brooches herself, after designing them and having them made when her cousin the King of Hanover was given many of her jewels.
The Queen inherited the brooches when she acceded to the throne in 1952, and has often worn them since.
She wore one to attend the funeral of Diana, Princess of Wales, in 1997, using it to accessorise a black jacket and matching skirt alongside three strings of pearl necklaces.
Her Majesty was joined by her family on the Buckingham Palace balcony
She also wore one on September 9, 2015, when she surpassed Queen Victoria as Britain’s longest-reigning monarch.
Now the Queen is the second longest-reining monarch in history, it makes sense that she would choose an item of jewellery with such a long royal history to mark the occasion.
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