Changing of the Guard is one of the oldest ceremonies connected with Buckingham Palace. In this process a New Guard exchanges duty with the Old Guard. I've witnessed it a few times over the years, always as part of a large throng of tourists waiting to take in the spectacle.
A Brief History of Changing of the Guard:
The military guard at Buckingham Palace is called The Queen’s Guard. The soldiers are drawn from one of the five regiments of Foot Guards in the British Army: the Scots Guards, the Irish Guards, the Welsh Guards, the Grenadier Guards and the Coldstream Guards. The regiments can be identified by how they wear the plumes in their hats and by their collar and shoulder badges.
(Note: Little did I know before I worked on this blog that the tall black hats worn with the red tunics are made of Canadian black bear fur. Each measures 18 inches and weights a pound and a half).
The Guard is commanded by a Captain, and each detachment is commanded by a Lieutenant. The handover is accompanied by a Guards band which may play a variety of music, ranging from movie themes to traditional military marches.
The Changing occurs in the forecourt of Buckingham Palace, in a fenced in area. It's almost impossible to get a spot by the fence so like most people, you'll likely just see the New Guard and band marching from Wellington Barracks into the palace forecourt -- then after a while the Old Guard and band depart from the Palace towards the Barracks or the Mall.
The ceremony is held about every other day (check with the Palace's calendar to be sure at the time you visit) and starts at 10:45, with the formal handoff occurring at 11:00 am. The New Guard takes over the responsibility of guarding the palace.
Excluding the time you spend waiting, the Changing takes about 45 minutes. It's all free, of course, so expect it to be busy. It's kind of fun to see the military precision, hear the music and commands being issued, and to be witness to a long-standing tradition. If I have any advice it's to arrive VERY early so that you can get a spot next to the Palace fence -- alternatively try to get an elevated view from the Victoria Memorial across from Bucking Palace.