The French had their Problems with descendants of immigrants rioting in Paris and Marseilles a couple of years ago. I can't remember how they dealt with it, but I'm sure they didn't stand back and watch like we are. We need Martial Law with the Army patrolling the London streets and a nightime curfew of 8pm for a few weeks until it all settles down again.
Anyone caught rioting and positively identified on CCTV footage should be sent to Afghanistan as IED fodder for the Taliban