Queen Elizabeth II’s funeral on Monday will be attended by more than 70 heads of government from around the world and poses the city’s biggest security challenge for Britain since World War II.

With as many as 2 million people expected to line the streets, and the royal family planning to walk in the open behind the Queen’s coffin, police are trying to strike a balance between safety and pageantry.

Presidents, prime ministers, kings and queens arriving from overseas add to the risk. Officials from the British domestic and foreign intelligence agencies, MI5 and MI6, are reviewing terrorist threats as part of the massive security team working on the funeral.

On Monday, snipers will be stationed on rooftops, surveillance drones will fly overhead and 10,000 uniformed police officers will be on duty, with thousands of plainclothes officers among the crowd. For days, police with bomb-sniffing dogs have been patrolling key areas. Private security guards will assist with crowd control.... Read More: Washington Post