They're changing guard at Buckingham Palace. The Queen wasn't in at the moment. We were not alone however -- every other tourist from the USA (and elsewhere) were there too. We have gotten used to being a novelty in Sydenham -- it was almost a surprise to find out that we aren't the only visitors.
In the same Westminster "neighborhood" we also visited St James Palace and St James Park and Whitehall, which used to be a palace and is now government offices. It is where Churchill's War Room was. (That's it at the end of the Buckingham Palace Mall Road in the fourth picture). St James is where Prince Charles has his offices.