Shaker Aamer, the last British resident to be held at Guantanamo Bay, is to be returned to the UK after 13 years at the US detention camp, the Foreign Office 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 US authorities in 2007 but was not freed.
His case was raised by British Prime Minister David Cameron during a visit to Washington in January and British lawmakers have called his treatment "inhuman."
"We have been notified by the US government that it has decided to return Shaker Aamer to the UK," a British Foreign Office spokesman said.
"The government has regularly raised Mr. Aamer's case with the US authorities and we support President Obama's commitment to closing the detention facility at Guantanamo Bay."
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 US military, according to rights group Reprieve.
He was then moved to Guantanamo which opened in 2002.
"In terms of next steps, we understand that the US government has notified Congress of this decision and once that notice period has been concluded, Mr. Aamer will be returned to the UK," the Foreign Office spokesman said.