Shaker Aamer, the last British resident held at Guantanamo Bay, will arrive back in the UK today after he was finally released from the controversial prison.
The 46-year-old is believed to be on a plane bound for London after 13 years in detention at the US military prison in Cuba.
Confirming his release, Foreign Secretary Philip Hammond said: "The Americans announced some weeks ago that they were going to release Shaker Aamer from Guantanamo and I can confirm that he is on his way back to the UK now and he will arrive in Britain later today."
Supporters said Mr Aamer will need medical attention once he arrives.
His US lawyer Cori Crider said: "We are, of course, delighted that Shaker is on his way back to his home and his family here in the UK.
"It is long, long past time. Shaker now needs to see a doctor, and then get to spend time alone with his family as soon as possible."
Mr Aamer, a Saudi national, has said he was originally seized by bounty hunters while working as a charity worker in Afghanistan in 2001 shortly after the 9/11 attacks.
He was handed over to US forces and in February 2002 he was transferred to Guantanamo Bay and accused of aiding al Qaida.
Campaigners spoke of their concerns that the father of four will be tagged or monitored by security services upon his return.
Lord Carlile, the former independent reviewer of terrorism legislation, told the Press Association: "The state cannot arbitrarily place restrictions upon him.
"It would be quite wrong to demonise him because there is no evidence to justify demonising him in 2015.
"I am sure there will be state authorities here who would like to interview him in the hope that he will provide them with some assistance in securing the safety of the public in this country.
"My view is that he should now be given the space to spend time with his family and catch up on all he has missed while he has been detained."
During his time in captivity, Mr Aamer's lawyers said he was subjected to torture, with beatings and sleep deprivation, and held in solitary confinement for 360 days. In 2005, he lost half his body weight during a hunger strike.
His family, MPs and actors Mark Rylance and Maxine Peake have also taken part in a 24-hour fast to show their support. Mr Aamer said he cried when he read about the protests.
He was described in US military files obtained by the WikiLeaks website as a "close associate of Osama bin Laden" who fought in the battle of Tora Bora. But in 2007 the allegations against him were dropped and he was cleared for release.
Despite a formal request by then-foreign secretary David Miliband, American authorities refused to allow him to go.
In letters, Mr Aamer said he was not sure if he would know how to respond to his name after being referred to as 239 - his prison number - for more than a decade.