Hi
While researching things to do in London I ran across the Ceremony of the Keys at the Tower of London tour. It was quite expensive but it looked kind of cool. Then I found out you can get tickets from the Historic Royal Palaces website for £5.
Tickets sell out fast and I mean fast. You can buy tickets for the next month on the 1st the prior month. The que opens at 4 PM London time, 7 AM PST here in the states. I got on the site a little before the opening time. I was able to pick the day I wanted, all days were open. So I picked March 29th and got two tickets. Easy enough.
About 15 minutes later I went back to the site and found me #1028 in the que with a 20 minute wait time. The cool thing is the site keeps your place in line so you can do other things while you are waiting. When I got back in almost all the weekends were sold out. That was about an hour after they opened ticket sales. So when they say it sells out fast they aren't kidding.
I thought I would pass this information along.