So many? First time anything like this has happened in London for 25 years.
Hooliganism is common place. Some form of riot happens every time Milwall plays West Ham, doesn't it? Which will be at least twice this season.
I assume you mean rioting outside or beyond the precincts of a football arena for purposes unrelated to allegiance to rival football clubs.
So many? First time anything like this has happened in London for 25 years.