Using the Rick Steve’s audio guide while walking through central London gives you a great perspective and history of the area.  The two tours that you will want to download are the Westminster Walk, and the City of London.  These walks you go at your own speed and stop in pub’s like Ye Olde Cheshire Cheese, The Clarence, and The George.  For Indian style food get to Bangladeshi Brick Town. Don’t forget Ben Franklin’s house.  For a free view of the city right by St. Catherine’s Cathedral go to the top of One New Change Mall using the elevator. For free higher views of the city get free reservations at the Fenchurch Skyscraper AKA the Walkie Talkie.  There is so much to do in this area that I just can’t mention it all.  Surely you will find even more that I know about so get out there and go exploring.