After arriving in London, I decided to start walking. And then I kept walking. 21 miles later there I was in my hotel room, cursing myself. While I felt fine that day, the next day was when everything decided to hurt. I spent that day hobbling to a little corner cafe for breakfast, then hobbling to a tiny market for snacks, and back to the room to watch bad English TV which turns out is mostly just bad American TV.
London was a very charming city, and I fell in love with how many parks there were as well as the fact that people actually used them. I would see people playing soccer or frisbee or flying kites or just sitting in the grass having their lunch. It was beautiful to see.
I recommend waking up early to take in all the sights, if that is your thing. I was there around 8 am and there was absolutely no one around. It allowed me to take my time everywhere, really soaking in the town. Buckingham Palace was a bit underwhelming. I think I expected to see the Queen out there mixing it up with us commoners. Big Ben snuck up on me as I was walking. Piccadilly Circus was quite busy the second time I visited; in the morning it was a ghost town.
Also: Mushy peas are awful.