Prince Louis joined his older brother and sister, Prince George and Princess Charlotte, on the iconic Buckingham Palace balcony to watch the flypast at Trooping the Colour.
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The youngest child of the Duke and Duchess of Cambridge was pictured pulling faces at the crowds, who gathered to catch a glimpse of the royal family to mark the Queen's official birthday.
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Prince Louis, four, who was stood next to his great-grandmother, the Queen, happily waved towards the sky and was then later seen holding his hands over his ears as the aircraft soared overhead, at which point his mum Kate was spotted bending down to have a word with him.
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Her Majesty could be seen interacting with Prince Louis – much to the delight of royal watchers. The monarch smiled throughout the flypast and waved at the crowds before going back into the palace.
© Photo: Getty ImagesAt one point Kate had a word with her son Louis
Other senior royals on the balcony included Prince Charles, the Duchess of Cornwall, and the Earl and Countess of Wessex along with their children.
Earlier on, the Cambridge children joined their mum Kate in their first carriage procession as historic celebrations marking the Queen's 70-year reign began during the four-day weekend.
Cheers went up from thousands of spectators on The Mall as they caught sight of the royal kids with proud parent Kate and the Duchess of Cornwall.
George, Charlotte and Louis smiled and waved enthusiastically as they sat in a row, with Louis, the youngest, in the middle of his older siblings.
© Photo: Getty ImagesThe young royal was seen holding his hands over his ears
The traditional carriage procession left Buckingham Palace ahead of Trooping the Colour, also known as the Birthday Parade.
Charlotte looked lovely in a cornflower blue dress, while her brother Prince George looked dapper in a blue suit. Prince Louis, meanwhile was adorable in a naval-style sailor suit.
