Prince Charles and Camilla met the crowds during a surprise walkabout after Trooping the Colour today.
The Prince of Wales, 73, even paused at one point to say hello to a teaching assistant before continuing to greet other spectators.
Caroline Hearn, from Hampshire, could be heard saying "it's amazing" while shaking Charles' hand. Footage then shows her jumping up and down in excitement while exclaiming: "He spoke to me!"
Charles' appearance came after he stood alongside the Queen on the Buckingham Palace balcony for a six-minute flypast marking the start of the extended Platinum Jubilee weekend.
Follow the Queen's Platinum Jubilee celebrations in our live blog here
Wearing sunglasses, the 96-year-old sovereign looked joyful as she surveyed the patriotic scenes, giving broad smiles as she enjoyed the aircraft display.
Earlier, she joined her cousin the Duke of Kent on the famous frontage to take a salute of her soldiers returning from Trooping the Colour, after the Prince of Wales deputised for her on the parade ground.
Eighteen royals including the Queen stepped out to watch the flypast, with Charles, Camilla, the Duke and Duchess of Cambridge and their three children Prince George, Princess Charlotte and Prince Louis taking centre stage on the balcony at Buckingham Palace.
The Queen leaned over to chat animatedly with her four-year-old great-grandson Louis, who at one stage covered his ears, and reacted with his mouth wide open and eyes tightly shut as the aircraft thundered overhead.
The six-minute flypast of more than 70 aircraft, including Apache helicopters, Typhoons and The Red Arrows, flew over the Palace.
Fifteen RAF Typhoons paid a special tribute to the monarch's record-breaking reign, flying in the formation of the number 70, prompting smiles from the Queen.
The Duke and Duchess of Sussex were among the guests who earlier watched Trooping the Colour at Horse Guards from inside the Duke of Wellington's former office, overlooking the parade ground.
They joined a host of more than 30 royals including Camilla and Kate and the Queen's extended family including all of her grandchildren.
It is believed to be the first time Kate and Meghan have met in person since the Sussexes left in 2020 for a new life in America.
The crowds were earlier treated to the sight of George, Charlotte and Louis with proud parent Kate and their step-grandmother Camilla in a carriage procession.
As the spectators waved at the young royals the trio waved back in their first major public outing for a Jubilee and first carriage procession.
The monarch, who has mobility issues, deputised her usual role to future king, the Prince of Wales, who inspected the Guardsmen in their scarlet tunics and bearskins and acknowledging their salute.
Thousands of wellwishers draped in Union flags, party hats and plastic tiaras flocked to London for the spectacle.
