Thousands met in Hyde Park today as part of annual global '420 ' event . The first day was a celebration for the legalization of marijuana, but it quickly turned into an anti-police rally with protesters throwing rocks and bottles at officers who were trying to keep them away from the park Controversial festival also saw gatherings in Manchester and Glasgow .
Thousands met in Hyde Park today as part of annual global '420 ' event . Crowds seen openly smoking marijuana as police officers stood nearby . Controversial festival also saw gatherings in Manchester and Glasgow .