The Metropolitan Police put on extra patrols, after a street party descended into violence in Brixton in the early hours of yesterday.
22 officers were injured and four people were arrested.
There were more clashes last night, with objects thrown at officers trying to shut down an event in Notting Hill.
Police used a helicopter to break up a mass gathering on Streatham Common.
Metropolitan Police Commissioner Cressida Dick says violence against Police officers won't be tolerated.