A Guantanamo prisoner who claims he was tortured at a covert CIA site in Morocco returned to Britain a free man Monday after nearly seven years in US captivity - the first inmate from the US prison camp freed since President Barack Obama took office. Binyam Mohamed flew to a British military base and was released after being interviewed for four hours by police and immigration officials. He had to fill out new paperwork for residency since his permit expired in 2004. Mohamed's claims of torture, abuse and extraordinary rendition are at the heart of several lawsuits. Lawyers on both sides of the Atlantic are suing for secret documents they say prove the United States sent Mohamed to Morocco and that Britain knew of the mistreatment - a violation under the 1994 UN Convention Against Torture. "I have been through an experience that I never thought to encounter in my darkest nightmares," Mohamed said in a statement released by his attorneys. "Before this ordeal, 'torture' was an abstract word to me. ... It is still difficult for me to believe that I was abducted, hauled from one country to the next, and tortured in medieval ways all orchestrated by the United States government."