Two police officers was hurt as violence overshadowed the second day of the Notting Hill Carnival.
A male PC, 33, was taken to hospital after being attacked during the event in West London, having been alerted to suspected drug dealing.
He was found in Lancaster Road at the junction with St Luke's Road at around 3.15pm yesterday with injuries to the head and torso, which are not thought to be life-threatening.
Meanwhile colleagues came under attack when they came to help him, and a 35-year-old female officer suffered injuries to her torso. She was taken to hospital but released yesterday, Scotland Yard said.
A man has been arrested for affray.