In about 48 hours, I'm going to be in london for what is essentially a day-long layover (long story, will explain soon). Any suggestions for things to do? ANY tiny little tidbit would be appreciated, from the most touristy/crowded/obnoxious monument to the most obscure/hidden specialty shop... I'm open to everything.
[for future reference -- a most pleasant new york experience, san francisco love, roman holidays]