The only UK politician I've seen up close was Tony Benn, many years ago. There's a bus stop on the corner near the House of Commons, and I was standing there waiting for a bus when he walked past in the street, perhaps three feet away from me.

I have been passed by the Queen while stopped in traffic, though. I could clearly see her in her car as it drove around the roundabout near St. Thomas' hospital, just across the river from the House of Commons, while my motorcycle was stopped at the head of the traffic coming onto the roundabout.

I've actually met Prince Phillip and exchanged a few words, albeit our conversation wasn't exactly profound.

Here in Washington DC there are lots of convoys of secret service cars, but you can't actually see who is inside past the tinted windows, so President Obama could go right past me (and probably has) but you can't tell who it is.