A police officer is airlifted to hospital following the crash, while a 26-year-old man is arrested.
A police officer has been airlifted to hospital after a crash involving a motorbike being driven the wrong way along the M25.
Kent Police said patrols were responding to a report of a stolen motorcycle when the collision happened near Junction 3 at about 16:05 GMT.
The male officer suffered serious injuries after being hit by the bike along the clockwise carriageway.
A man, 26, was arrested on suspicion of offences including dangerous driving.
The M25 was closed in both directions near Junction 3 for Swanley after the crash.
Both carriageways have since reopened but police warned drivers to expect delays.