Shaker Aamer, the last British detainee at Guantanamo Bay, has been released, it has been confirmed.
Mr Aamer, who has been detained without charge at the Cuban prison facility since 2002, is believed to be on a flight back to the UK.
Sources within his legal team said he was due to land at a UK airport at around lunchtime on Friday.
In September, the US government notified UK authorities of their intention to return Mr Aamer to Britain.
He has a wife and four children living in Battersea, south London.
The 46-year-old Saudi national was originally detained in Afghanistan in 2001 while working as a charity worker.
He was subsequently transferred to Guantanamo Bay where he has been held without charge.
His lawyers say he has been subjected to torture, beatings and sleep deprivation during that time.
Earlier in October, celebrities and politicians took part in a 24-hour "hunger strike" to keep up pressure for his release.
Among those taking part were actors Mark Rylance and Maxine Peake, MPs David Davis and Andy Slaughter and the prisoner's lawyer Clive Stafford Smith.
In March, MPs debated his detention in the House of Commons, with former ministers Mr Davis and Andrew Mitchell among those voicing concerns about the situation.
Andy Worthington, co-director of the We Stand With Shaker campaign, said he had informed by Mr Aamer's lawyer that he is due to return to the UK today.
He said: "We're delighted to hear that his long and unacceptable ordeal has come to an end.
"We hope he won't be detained by the British authorities on his return and gets the psychological and medical care that he needs to be able to resume his life with his family in London."
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