One day and one night in any new place isn't nearly enough time, but with careful planning and strong coffee you can certainly experience its highlights.
We took the red-eye from New York to Gatswick, and learned that a dinner of ZzzQuil and water is not a strong enough strategy to get a good night's sleep on a plane. But because we couldn't check into our hotel until later in the afternoon, we did an airport restroom clean-up, paid way too much to store our bags, and headed to London.
We did almost everything we wanted: saw Big Ben and Westminster Abbey, experienced cute local pubs, wandered old neighborhoods, walked through St. James's Park to the Buckingham Palace, and ate meat pies (Lorenzo's wish ever since he saw Sweeney Todd). As a die-hard Beatles fan I was bummed we missed Abbey Road, but that's reason enough to return someday!
London was a lot quieter and cleaner than I was expecting. Maybe it was just the area we were in, or the fact that in my mind I was imagining a city like NYC blended with scenes from Oliver Twist and Mary Poppins. Regardless, it's a lovely place and we can't wait to visit again.