The Briton Bisher al-Rawi is expected back in London this weekend after four-and-a-half years held captive in Guantanamo Bay.

Mr al-Rawi, 39, of New Malden, Surrey, was arrested by the CIA in the Gambia in November 2002 and has been held at the Cuban airbase by the US Government ever since without trial, under suspicion of having terrorist links.

Foreign Secretary Margaret Beckett announced the news in Parliament on Thursday that Mr al-Rawi would be released and brought home to the UK within three days, after lengthy negotiations between UK and US governments.

Kingston and Surbiton MP Edward Davey who has campaigned for his release for several years, said: "I am relieved that the nightmare for Bisher and his family is finally over. He will have been in prison for nearly five years, without charge or trial, against all the rules of natural justice and against all the legal traditions."

Mr al-Rawi, an Iraqi citizen, fled from Saddam's regime with his family when he was 16 and they settled in New Malden. As the youngest son it was decided he would not take British citizenship in the hope the family could one day reclaim assets in Iraq.

He was arrested in 2002 on a business trip to the Gambia with his brother Wahab and friend Jamil el-Banna, who were planning to set up a peanut factory. After weeks of questioning, Wahab was released while his brother and friend - both only British residents - were flown to Cuba and imprisoned in the US airbase.

Mr al-Rawi has claimed he was helping MI5 before his arrest, acting as a go-between to communicate with radical Muslim cleric Abu Qatada - a family friend of the al-Rawi's through their local mosque.

Wahab al-Rawi, 41, made an appeal in the Surrey Comet in January for the release of his brother. He said: "There are probably dangerous people in Guantanamo - the world is full of mad and dangerous people and we should be protected from them. But Bisher is not one of them."

Mr al-Rawi's lawyer Zachary Katznelson from the Reprieve charity welcomed the news of his release, and said he did not expect him to face UK charges.

He said he spoke to Mr al-Rawi several weeks ago about his possible release, and added: "He said, Don't worry about me, it is Jamil el-Banna who is important. If I am leaving, they should be leaving with me.' "He wants to work on their behalf to help bring them home. He wants to have some time with family and re-establish his life. He has been away for so long."

Mr Katznelson said he expected Mr al-Rawi to be taken to a private location, but did not know any further details of his release.

Of Guantanamo Bay, he said: "I have seen the prison with my own eyes and it is brutal. All but one are kept in constant isolation, living in six by eight foot steel cells, with no windows and unrelenting electric light.

"One has been on hunger strike for over 100 days - tied down and force-fed twice a day. Just like Bisher, none of them are charged with a crime."

Edward Davey condemned the prison and the treatment of Mr al-Rawi. He said: "Everything I've learnt from his family, his lawyers, UK Government officials, journalists and even the US authorities, actually tells me that Bisher is not and has never been a threat to national or international security.

"His case should be a lesson to everyone that when you ignore the due process of law, injustice follows. I hope he and his family can now be left to rebuild their lives after this harrowing ordeal."