In 2005 I visited London on my Contiki trip. I had a long list of things I wanted to do, but only a day and a half to do them all so I had to pick selectively. I decided the second thing (the first was the changing of the guard at Buckingham Palace) I wanted to do was the Tower of London because I wanted to see the crown jewels. I'm really not into jewels for myself, but they are fun to look at.
Shortly after I got there a tour was starting with one of the Yeoman/Beefeater so I took that tour. The first thing I remember learning was what their uniform means, or what the insignia "EIIR" means - Elizabeth The Second Reigns. This insignia will change when there is a new monarch in England. I distinctly remember it being a cool and rainy day (shocking!) in London, and it rained during the tour. But the Yeoman was friendly and continued on with the tour. The official records show that 300 or so people were killed or tortured in the Tower of London, but they found the remains of over 1000 people under the church, hmmmm. Today the moat is empty, apparently stuff tends to accumulate there when it has water so they leave it empty. Rumor has it that the Tower is haunted, the most haunted building in all of London. I didn't see any ghosts, but then they might just know that I'm afraid of them and steared clear of me.
After my tour, which was excellent and informative about British history, I went to see the crown jewels. They don't advertise it, but I believe they're all copies. But it was still fun and interesting to see, they are quite impressive. I didn't know that there are different crowns, they don't all wear the same crown to the coronation. They're all quite similar but there were so many different ones that it actually became confusing.
In hind site I don't know that I would put the Tower of London as my first thing to see, or even my second. I'm kinda sorry that I missed Westminster Abby, I suppose that just means that I have to get back to London one of these days. But the Tower of London is worthy of a top 5 things to do in London, so if you have more then 1 day in London, add it to your list.