Michael Phelps, Nathan Adrian, Matthew Grevers and Brendan Hansen of the U.S. hold a banner thanking host city London, after receiving their gold medals for the men's 4x100m medley relay final, during the London 2012 Olympic Games at the Aquatics Centre August 4, 2012. REUTERS/Toby Melville (BRITAIN - Tags: SPORT SWIMMING OLYMPICS TPX IMAGES OF THE DAY)