There are a few parks surrounding Buckingham Palace that used to be part of the palace's grounds but are now open to the serfs. St. James' Park is the prettiest, and provides the best vantage point for photos as well. We didn't tour Buckingham Palace because it's only open during the summer, but I've done it previously. I would definitely recommend it but mainly because you'll feel like you missed something on your tourist checklist if you didn't. But it's not really that interesting. It's grand but not over the top enough to be memorable, and it's scrubbed of any sense of someone actually living there. There was a tv show about the real life at the palace, and people working there would talk about the queen eating cereal out of tupperware containers and stuff like that. Now that's a tour I'd like to take.