I would also have to say that Marriott Grosvenor Square is also a great hotel for a first time London visitor. It was the hotel where I stayed the first time that I visited London, and have stayed there on other occasions too. GS is 1 block from the Oxford/New Bond Street station, which is across the street from Selfridges, the flagship store of a nice luxury department store chain, in London's Oxford Street is the second largest store in the UK (after Harrods), and central to most everything in London. It is on the same square as the present US Embassy (there will be a new US Embassy built starting in about 2012 in a different location), and is a truly great neighborhood for walking.