The final British prisoner held in Guantanamo Bay will be released and returned to the UK.
Shaker Aamer was seized in Afghanistan and taken to the US facility in Cuba in 2001, where he has since been held without charge.
The 46-year-old was born in Saudi Arabia, but his wife and four children are British citizens.
Mr Aamer has been the subject of a long campaign to secure his release.
The US government has notified the UK authorities that it now intends to return him to Britain.
His release is expected to take place once the 30 day notice period set by the US authorities has expired.
Amnesty International UK Director Kate Allen said the news of his return was a "huge relief".
She said: "In the past Mr Aamer has reportedly been at death's door during a hunger strike and his return to his family in Britain won't come a moment too soon.
"The immediate focus should now be on providing medical and other support for Mr Aamer on his return to the UK, but let's not forget that his 13-year ordeal at Guantanamo has been an absolute travesty of justice."
A UK government spokesperson said: "The Government has regularly raised Mr Aamer's case with the US authorities and we support President (Barack) Obama's commitment to closing the detention facility at Guantanamo Bay.
"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."
Shadow Justice Minister Andy Slaughter, said: “This is a welcome decision to release Shaker Aamer from Guantanamo. His continued detention was an affront to the rule of law.”
Aamer, a Saudi national living in London, was seized in Afghanistan and rendered to the US facility in Cuba in 2001.
He never charged, and was cleared for release in 2007.
Jeremy Corbyn was part of delegation of British MPs who flew to the States in May to lobby for Mr Aamer's release.
The Labour leader joined former Tory International Development Secretary Andrew Mitchell and Conservative MP David Davis on the visit to Washington DC.
On July 4 - Independence Day - a host of Hollywood stars, musicians and politicians called on Mr Obama to release him.
In an open letter to the US president, actors including Ralph Fiennes and Sir Patrick Stewart and musicians such as Peter Gabriel joined mounting calls for him to be freed.
London mayor Boris Johnson and comedian-turned-activist Russell Brand were also among more than 90 people who signed the letter, published in the Guardian, to coincide with the US public holiday.
Pink Floyd star Roger Waters took part in a protest outside the US Embassy in February over the case, and said Mr Aamer's imprisonment without trial was an affront to the democratic values Britons died defending during the world wars.
He said: "As far as we know, this is an innocent man who has been held for 13 years. They refuse to explain why they are holding him, not even to the Prime Minister or Great Britain.
"The idea is that we are at war with terrorism and if you drag in some innocent people and they die, so what? You do not care.
"The rights of the individual are being ridden roughshod over by these Neo-Conservatives.
"It is appalling that there is a woman and four children living in London and their beloved father and breadwinner has been locked up and treated remorselessly.
"Anyone who has had any conversations with Shaker is impressed he has not turned bitter or angry. He has retained his humanity.
"In England in the 17th Century, and France and America in the 18th Century, we stood up for the idea that all human beings have rights."
Others who demanded his release included poet laureate Carol Ann Duffy, Sophie Ellis-Bextor and Bianca Jagger.
Last year he gave an interview to US TV show 60 Minutes.
Shouting from his cell he said: "Tell the world the truth ... Please, we are tired. Either you leave us to die in peace - or either tell the world the truth. Open up the place. Let the world come and visit. Let the world hear what's happening.
"Please colonel, act with us like a human being, not like slaves."
He added: "You cannot walk even half a metre without being chained. Is that a human being? That's the treatment of an animal...
"It is very sad what is happening in this place."
Copyright © 2021 Trinity Mirror Group