Another question, I'm assuming you can run through the subways (what we in the US call underpasses), especially between Green Park and Hyde Park? Are there ramps or do you go up/down stairs?

I took a look at some routes, and I'm simply amazed. Getting to run is one thing, but running past Buckingham Palace (if I do it) is something I'll be able to tell people about.

Does anyone have any experience swimming with the Serpentine group? I had already contacted Otter swimming as I had swum with them when I was in London last, and I had great experiences. I swim with a Masters Swim team here, basically a swim team for adults. The nice thing about Otter was that it wasn't just triathletes, and the workouts had some variety (not just freestyle). It was challenging swimming down the other side of the lane though.