The Duke of Cambridge joked that he was like "giraffe on ice" on a football field during a visit to an academy school in south-east London.
He said: "Watching me on the football field is never a pretty sight – the expression giraffe on ice springs to mind.
"However it is marginally less embarrassing than seeing my brother cheat his way to becoming the fastest man on the planet!
"Catherine, on the other hand, with a tennis racquet or a hockey stick is something to behold and be aware of."
The royals visited the academy school to attend the launch of a new project that is being supported by their charitable Foundation.
More top news
Police have launched an investigation after a woman found a hidden camera while in the shower at a Travelodge.
A plumber who virtually decapitated his girlfriend with a breadknife has avoided a murder trial - because he is an alcoholic.
A man who opened a parcel addressed to his new home was shocked to discover a large tarantula inside.