Shaker Aamer, the last British resident to be held at the U.S. prison camp in the Guantanamo Bay navy station in Cuba, has been freed after 13 years in detention, Britain said on Friday.Aamer, a Saudi national who is married to a Briton, was never charged with any crime and had been cleared for release by U.S. authorities in 2007 but was not freed.Last month Britain said Aamer was due to be released but no date was specified."I can confirm that he is on his way back to the UK now and he will arrive in Britain later today," Foreign Secretary Philip Hammond said.Aamer moved to Britain in 1996 and was in Afghanistan doing voluntary work for an Islamic charity when he was captured by Afghan Northern Alliance forces in 2001 and handed to the U.S. military, according to rights group Reprieve.He was then moved to Guantanamo, where the prison camp was opened in 2002.