London Mayor Boris Johnson, center, poses for pictures with fans of Britain's team following a photo-op with London ambassadors, the volunteers working around the city to give tourists directions and information, in central London, Tuesday, July 31, 2012. After meeting Tuesday with the volunteers, Johnson firmly denied media reports that he was trying to capitalize on the goodwill churned up by the games to catapult himself into the prime minister's chair. (AP Photo/Lefteris Pitarakis)