This is on many lists that people want to see during their time in London. The Changing of the Guard is a ceremony that involves a new guard exchanging places with the old guard on duty.
The official start time of the ceremony is 11.30am, though the music starts at 11.15am, so if you want to see the whole thing, be sure to arrive for that time. During the summer, plan to arrive slightly earlier due to crowds.
If you want to see this you’ll need to plan ahead, especially if you are visiting outside of the summer season as it is not as regular, nor are the regiments which rotate on a montly basis. Dates and times can be found here.
If you can’t see it at Buckingham Palace, the ceremony also takes place at Windsor Castle (11am) and the Horse Guards Arch (11am and 10am on Sundays).
I’m all one for traditional and prompt-ness so I was surprised to find that the day I attended, they were running 15 minutes late. This wasn’t aanounced, I just noticed the time. However, the ceremony started, a very orderly affair and not rushed due to delay, everything in its time and place. Depending on where you stand, it might be hard to hear what is being shouted, so try and get as close to the hut as you can, behind the gates of course. The ceremony isn’t long, so once it is finished you can use the rest of the day to explore London.