London Pass

List out the places you want and calculate how much they would cost without the pass. Aside from that, I found it convenient because it enabled me to carry less cash or use my card less. But for two days you may have to rush around to make it a deal.

Randy,
It's been 4 years since I looked at the pass options so things may have changed, but I doubt it. I agree with the previous response that you must add up the charges of the sites you'll definitely go to and see if the pass covers the costs. One warning: I noticed the Pass advertising listed things as covered that were actually free to begin with. Most often, a museum with free admission already would give you a free audio guide with the pass. When calculating the costs of admission to sites, don't rely on the info given to you by people looking to see a pass. Check the admission rates in the Rick Steves' guide or go directly to the sites' web pages instead. In 2009, my wife and I determined that the pass was NOT worth it for us.

Should I pre purchase tickets for tower of london by e-mail to get a fast track entry-or just go early when it opens?

Personally I think the London Pass is not really worth it. You feel like you have to RUSH to get your money's worth. I would rather pay a little more and move at my own pace. For some of the sights you have to get in line with everyone else even if you do have the pass.
We were just at the Tower a couple of weeks ago. It was a cool, cloudy day and we got there around 9:30. No lines at all for the ticket booths and the line to get in took about 3 minutes. Went straight to the Crown Jewels and then into the main tower to see the armor and then around to the rest of the parts of the castle. By the time we left around 12 it was extremely crowded. Just get there when they open and you should be fine!

Randy, Do the math as and determine if it suits your needs/pocketbook. i do the math everyplace i plan on going and if they offer such a pass. Sometimes its a wash, sometimes its not. If the pass covers transportation, you have to put a $$$ on that too. When i was in london last year, i got the pass. I was able to use it and then some, but i enjoyed not having to wait in some lines. happy trails.

I did not do the pass but on occasion envied the folks who did. Tower of London ticket office is pretty well organized and if you get there early not too bad. Just be aware it is north of the Tower and not at the entrance. I came around the Tower Bridge side and spent time walking all around to get to the ticket office. The London Pass would have saved me 15-20 minutes at St Pauls. I agree that you will need to rush to break even. We rushed too much and I think it detracted from the enjoyment of the trip.