Shaker Aamer is reportedly set to take legal action against the Government following his release.
Amir, the last British resident held at Guantanamo Bay, is marking his first full day of freedom back in Britain after being held for 13 years without charge at the US military facility in Cuba.
It is understood the father of four, who is receiving treatment in hospital, has already been reunited with his wife Zin.
He is due to meet his children this weekend, including youngest son Faris, who was born on day Aamer arrived at the notorious US military prison.
Shaker Aamer spent 13 years at Guantanamo Bay
It is thought that he is now going to bring legal proceedings against the British Government over its alleged complicity in his mistreatment, the Press Association reported.
A source said: "Proceedings were initiated some years ago on his behalf that could not be followed until his return to the UK.
"They will now, undoubtedly, be progressed."
The source added that rumours that Aamer could receive £1 million were “speculation”.
Clive Stafford-Smith, of human rights group Reprieve, called for an independent inquiry into allegations that Aamer was tortured at Guantanamo.
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He told BBC Breakfast: "We had a promise from the Prime Minister that there would be a fully independent inquiry into all of this torture. Unfortunately that's not happened yet.
"This is a huge priority of Shaker's. He doesn't want to have people persecuted. He doesn't want to have small people, who were sent out to do their jobs, prosecuted for what they did.
"What he does want is that the whole world should know what did happen so we can set in place rules so that British agents and, let's hope, American agents don't get involved in the torture business in the future."
Aamer is suffering from a number of medical conditions including post-traumatic stress disorder, one of his lawyers, Ramzi Kassem, told BBC Radio 4's Today programme.
The 46-year-old arrived on a private plane at Biggin Hill airport in south-east London yesterday afternoon.
Aamer landed in London on Friday
Aamer 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.
The Saudi national was handed over to US forces and in February 2002 he was transferred to Guantanamo Bay and accused of aiding al Qaida.
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.
Aamer’s lawyers say during his captivity, he was tortured and held in solitary confinement for 360 days. In 2005, he lost half his body weight during a hunger strike.