what makes this visit for president and mrs. obama particularly special? joining us now to provide some historical context to the visit is our own martin bashir. thanks so much. you know this better than all of us. tell us, the pomp and circumstance, all of the gun salutes, and how complicated ht all was, i was reading some of the historical background, what is so special about this day for president and mrs. obama? >> it is interesting. the relationship between america and the united kingdom is described often as a very special one. but you may not know that since elizabeth succeeded to the throne in 1952, she has met all 12 american presidents. in fact, she's met all 11 because she didn't meet lyndon johnson after the assassination of john f. kennedy, but apart from that, she's met all 11 in that period. so she's been a mainstay in this relationship. and, of course, each leader, each president has visited, romd reagan in 1982, bill clinton,