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A police car overturned while officers were chasing a moped believed to have been involved in a "series of offences".
Officers in a marked vehicle followed the moped rider and pillion passenger for about half a mile from Hyde Park Corner in central London at 04:30 BST.
The moped then crashed with a second marked police car travelling in the opposite direction which overturned.
A 17-year-old boy was taken to hospital with serious leg injuries.
He has since been arrested on suspicion of a number of motoring offences, the Met Police said.
Officers said the second person on the moped fled the scene of the crash in Grosvenor Place and efforts to trace him are ongoing.
No police officers were seriously injured or required medical treatment, the Met added.
The crash has been referred to the Independent Office for Police Conduct and the Met's Directorate of Professional Standards has been informed.