Ceremony of the Keys

I'd check with another post office....maybe they just don't have them in stock there, or they can't be bothered filling them out. They are apparently still available, at least according to the USPS site...http://pe.usps.gov/text/imm/immc3.6.25.htm#ep28655

I went to the ceremony, it was just OK only. We were not invited into the tower. However strolling the tower bridge at night was beautiful and seeing the night lights at the tower. It might be more special for children. We got there 45 min ahead which too much.

I found it quite interesting when I attended it in the 90's. Viewing the Tower is not part of the ceremony, as it closes to the general public several hours before then. You have to remember that The Tower is not just a museum but the home of the Yeoman Warders. I would arrive about 15-30 minutes prior to the start. Since the quantity of tickets is limited, it's not necessary to get there exceedingly early. The Ceremony is essentially the locking of the Tower for the night. If you are willing to risk a spoiler, this website (http://www.trooping-the-colour.co.uk/keys/index.htm) explains the ceremony.

I hope that this is helpful!

My daughter and I did the Ceremony on our Sunday night in London, when no theaters were open. We enjoyed it very much. Our guide gave us a good introduction to Tower history; we ended up going back for a daytime tour to see more of it [and hear another Yeoman; they're very entertaining]. We got there about 3 minutes ahead of time which was way too stressful; underestimated how much time it would take us to walk over from near the Globe and ended up running most of the way around the Tower so we wouldn't miss out. Therefore I agree with the poster who suggested you try to arrive 15 minutes ahead.

Its free and on a sunday fun activity been 3 or 4 times (in 40 years )