A police officer has been seriously injured by a car in Bexleyheath, south-east London, while chasing a man suspected of assaulting a woman.
The officer responded to concerns raised for the safety of the woman on Mayplace Road West at about 12:00 GMT.
The car was not linked to the alleged assault, and the driver is understood to have stopped to assist police.
The officer was taken to hospital where he is being treated for serious injuries, the Met Police said.
A man was arrested near Bexleyheath Police Station on suspicion of domestic common assault.
Road closures currently remain in place.