British authorities agreed to the creation of a “sterile zone” around the President with a series of road closures in central London and a security cordon keeping the public away from his cavalcade. The American had also wanted to travel with a mini-gun, which usually forms part of the mobile armoury in his cavalcade. It’s fired from a tank and could mow down hundreds of terrorists on the President’s say-so. This is especially helpful during peacekeeping deployments.