Emirati President Sheikh Khalifa bin Zayed al-Nahayan arrives to pay a visit to Prince Charles, Prince of Wales, at Clarence House in central London on May 1, 2013 on the second day of his state visit to Britain. The UAE president was to face questions from Prime Minister David Cameron over allegations that three British men jailed in Dubai were tortured. AFP PHOTO / POOL / JOHN STILLWELL        (Photo credit should read JOHN STILLWELL/AFP/Getty Images)