Mr Aamer, who claims he was subjected to 300 beatings in the camp, flew into London's Biggin Hill airport on a private plane this lunch time.

He has been held in the prison - which is part of huge US naval base in Cuba - for 13 years without trial.

The prison has detained about 750 people since it opened as part of America's "War on Terror" in 2001. It currently holds about 120 inmates.

Mr Aamer's case was debated in Westminster in March and MPs lobbied Washington to speed up the transfer, which was cleared in 2007.

Cori Crider, Mr Aamer's US lawyer, said: "Shaker now needs to see a doctor, and then get to spend time alone with his family as soon as possible."

Mr Aamer was originally detained in Afghanistan in 2001 and accused of having links to al Qaeda.

He was described in US military files 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.

He claimed he was seized by bounty hunters while working as a charity worker shortly after the 9/11 attacks

A spokesman for David Cameron said the Prime Minister welcomed the release.

Mr Aamer will no longer be detained and will "be free to be with his family", the spokesman said.

Shadow chancellor John McDonnell, chair of the Shaker Aamer All-Party Parliamentary Group, said he was "breathing a heavy sigh of relief". 

"Shaker was simply a man in the wrong place at the wrong time, a charity worker building wells in Afghanistan who was  kidnapped, ransomed and falsely imprisoned," Mr McDonnell said.

Labour leader Jeremy Corbyn tweeted: "Great news. Huge congratulations to his family."

Meanwhile, Green MP Caroline Lucas, who undertook a fast last week for 24 hours to show her solidarity with Mr Aamer, welcomed  his return.

"The Government and security services must now guarantee the safety of Shaker and his family upon his arrival home," she said.

Mr Aamer was born in Saudi Arabia but has British residency. His wife and four children live in London.

Andy Worthington, co-director of the We Stand With Shaker campaign, said the "long and unacceptable ordeal" had come to an end.