And now from the other direction...
After allowing traffic to resume for a couple minutes, the Bobbies shutdown the approaches to Buckingham Palace once again in order to allow another group of soldiers to come marching in from another sidestreet. Unfortunately I never learned what regiments these troops served in. Whether they are Coldstream Guards, Grenadier Guards, Irish Guards or Scots Guards, when they are on duty guarding the palace, they are called "The Queen's Guards".