I think I may have gone overboard with this. I got talking to a clerk in a travel shop, and he persuaded me it would be a good idea to take precautions. I bought a waist wallet and a special purse. I even convinced Mr. M to get a man bag. That was a bit of a hard sell, but I told him to think of it as a camera bag--and he did carry his camera in it.
Did we need this stuff? Not sure. I did pick up a brochure at St. Paul's that warned about pickpockets, but I didn't feel any more at risk in London than I do in D.C. or New York. I didn't bother with the waist wallet, but I was happy to have the purse. It wasn't at all stylish, but it gave me piece of mind. It had a handy exterior pocket for my Oyster card and was big enough to hold pretty much everything I needed--camera, scarf, gloves, sunglasses, and most of the research books I bought.
And now that we have this stuff...I guess that means we need to take more trips, eh?