The London Pass

Probably not. You have to do the math yourself, but it's unlikely that you will get your money's worth from it. So many of the major attractions are completely free, and you can't do everything in four days. Look at admission prices for the things you absolutely want to do/see, and think about how long each thing will take, so you don't overbook yourself. (Passes usually list a lot things you wouldn't want to see anyway - or don't have time for - to make it look more valuable.) Then just see if it makes sense to get the pass.