To celebrate Prince William turning 39 on Monday, Clarence House have released a photo of the Duke of Cambridge as a baby, in the arms of his father.
The image of Prince Charles holding his son was captured in December 1982, when the Duke was just six months old.
The milestone comes a day after he appeared at a local running event with his two eldest children to celebrate Father's Day.
George and Charlotte were photographed wearing shorts and trainers, while the Duke was dressed in a blue shirt and a pair of navy chinos.
One runner couldn't believe his eyes that Prince William and his children attended the running event, Kev Richard tweeted: "Running at Sandringham this morning in a half marathon and the race starter was none other than HRH Prince William. Ha! Just two future Kings behind me."
According to the event’s website, Run Sandringham was welcoming hundreds of runners of all abilities and ages to run a half marathon, 5K or community mile, with the aim of raising “many thousands of pounds for good causes”.
It is understood the Duke was not running in the event and was there in a private capacity.
Prince William's life:
Prince William Arthur Philip Louis of Wales was born second in line to the throne at St Mary’s Hospital, Paddington, at 9.03pm on June 21, 1982.
He weighed 7lb 1 1/2oz and was the first born son of the Prince and the Princess of Wales.
At just nine months old, he accompanied his parents on their six-week official visit to Australia and New Zealand, which was a break from royal tradition.
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He was just 15 and Harry 12, and the brothers walked behind the princess’s coffin during a funeral procession through London.
William met Kate Middleton at St Andrews University in Fife, Scotland, and the pair wed in 2011 after dating for more than eight years.
He was made the Duke of Cambridge by his grandmother the Queen on the morning of his wedding.
The couple welcomed their first child George – also a future king – in 2013, followed by Charlotte in 2015 and Louis in 2018.