British Prime Minister David Cameron has asked a former New York and Los Angeles police chief to help tackle Britain's gangs, who were alleged to be the main culprits of the riots in London and some other cities. Mr. Bill Bratton is expected to explore the U.S. experience in dealing with gangs and share what might help the British government prevent similar incidents in the future. Bratton made great achievements in reducing gang crimes in both New York and Los Angeles. In his first two years as head of the New York police department, reports of serious crime dropped by 27 percent. So far, about 1600 people have been arrested after days of riots and looting in London and some other Britain's cities, with 698 now facing charges.