Britain will not allow a culture of fear to take over the streets, Prime Minister David Cameron insisted Wednesday, saying police have drawn up contingency plans to use water cannons if necessary. “We will do whatever is necessary to restore law and order onto our streets,” Cameron said in a somber televised statement. “Nothing is off the table.” Cameron has already recalled Parliament from its summer recess for an emergency debate on the riots Thursday. Thousands of extra police officers on the streets kept a nervous London quiet Tuesday night after three nights of rioting, but looting flared in Manchester and Birmingham, where a murder probe was opened when three men were killed after being hit by a car. Eerie calm prevailed in the capital, where hundreds of shops were shuttered or boarded up as a precaution, but unrest spread across England on a fourth night of violence by brazen crowds of young people. Scenes of ransacked stores, torched cars and blackened buildings have frightened and outraged Britons just a year before their country is to host next summer's Olympic Games, bringing demands for a tougher response from law enforcement. Police across the country have made almost 1,200 arrests since the violence broke out over the weekend. In London, where armored vehicles and convoys of police vans patrolled the streets, authorities said there were 16,000 officers on duty — almost triple the number present Monday night. The show of force seems to have worked. There were no reports of major trouble in London, although there were scores of arrests — almost 800 people in the capital since violence began Saturday. “What happened in London last night was, when community leaders and the police came together, there were significant arrests,” said police deputy assistant chief constable Stephen Kavanagh. “Some looters were taken away before they got into doing anything, but it was that joint action that made the difference.”