The royal trio laced-up their trainers and took to the track at the Queen Elizabeth Olympic Park in east London for their mental health campaign Head Together.
Joined by around 150 runners, William, Kate and Harry competed against one-another for the 50 metre sprint. Kate, who wore a red puffer jacket and black jeans, tied back her hair on the start line alongside her husband.
Despite an impressive sprint, the Duchess was beaten by both William and Harry who were wearing chinos and trainers (Not fair (lol)
The training day was organised for runners taking part in the marathon for Heads Together an umbrella organisation spearheaded by the three royals.
It aims to change the national conversation on mental well-being to a positive one, and is a partnership between eight charities that provide front-line mental health support.