Shaker Aamer will not be detained once he returns to the UK, Downing Street has said.
However, the Prime Minister's spokeswoman said measures had been put in place to "ensure public safety".
"As soon as he is returned to the UK he is no longer in detention. He is free to be reunited with his family," she said.
"The Prime Minister has been clear that the public should be reassured that everything to ensure public safety is in place."
She added that David Cameron welcomed Mr Aamer's release after he raised the issue personally with US President Barack Obama.
Who will mourn Guantanamo Bay? Hardly anyone.
Shaker Aamer spoke to ITV News last week via his lawyer in his final interview before his release from Guantanamo.
Shaker Aamer, the last British detainee at Guantanamo, has been put on a flight back to the UK. Here's what we know about him.