Mayor of London Boris Johnson is the author of "Life in London: The People Who Made The City That Made the World". Johnson selects several character from history whom, in his opinion, have made London the great city it is today. One of his picks is Rolling Stones guitarist Keith Richards; partly because of his creative genius and partly because under his influence, the Rolling Stones were able to give back the blues to America. The full show of Allan Gregg in Conversation airs Saturday July 21st at 6.00 pm