on dealing with crowds, we are looking also at the use of existing dispersal powers and with any wider power of curfew is necessary. mr. speaker, whenever the police face a new threat, we must have the freedom of the confidence to change tactics as necessary. they must have the political backing and support to do so. now the work begins of rounding up even more of those suspected in the violence. nbc s martin fletcher is in london with more details. reporter: well, the rioting is pretty much over. now is the time of reckoning. police operating all over the capital, arresting suspects identified as looting, stealing, setting fires, attacking police and other crimes, and prime minister david cameron said the police will find and punish the guilty. he also said he will ask america for help, that britain can benefit from america s experience fighting gangs. 1200 people arrested so far, half of them under 18. security camera pictures are being circulated with the public