Benedict Cumberbatch and Jude Law are among a host a celebrities who have recorded readings from the diary of a Guantanamo Bay detainee.

Narrations by the actors from Mohamedou Ould Slahi's account are being released today to mark the publication of a book based on the journal, as well as a campaign for him to be freed after being held in the prison camp for more than a decade.

Readings by other high profile figures including the author Philip Pullman, actor Dominic West and musician Brian Eno are set to follow in the coming days, while recordings featuring Stephen Fry and Colin Firth have already been released.

Slahi, who was born in Mauritania, West Africa, has been detained at Guantanamo Bay without charge for more than 12 years.

The 44-year-old spent around a year fighting with the mujahideen in Afghanistan against the Soviet invasion in the early 1990s.

He pledged his allegiance to al Qaida in 1991 but has always maintained he cut all ties with the group a year later.

However, he was arrested in the aftermath of the 9/11 attacks and in 2002 he was moved to Guantanamo Bay, where he remains today.

He is still being held despite a ruling by a judge in 2010 that he should be released, his legal team say.

His diary, which contains details of harsh treatment and alleged torture he was subjected to at the Cuban detention centre, was the subject of a seven-year legal wrangle as his lawyers battled the US government for it to be released.

The 466 page account was finally cleared in 2012, albeit with more than 2,500 redactions.

It has been released as a book titled Guantanamo Diary in the UK today and will be published in 20 countries. It is believed to be the first book written by a detainee of the facility who is still imprisoned.

At a press conference in London today to launch the book and a campaign for the detainee's release, his younger brother Yahdih Ould Slahi said: "If you read the book you can see every line, every word is written with the blood and tears."

He described his family's pride in the publication of the book. "He gave a voice to all the people that are suffering in similar situations," he said.

Larry Siems, the editor of the book, described Slahi as "one of the most abused prisoners in Guantanamo" and said his writings detail "harrowing" treatment.

In one section, Slahi described being subjected to a "session of torture and humiliation".

He said: "The torture squad were so well trained that they were performing almost perfect crimes, avoiding leaving any obvious evidence.

"Nothing was left to chance. They hit in pre-defined places. They practised horrible methods, the aftermath of which would only manifest later."

Nancy Hollander, a member of the prisoner's legal team, recalled her first meeting with him.

"There was this small man standing there smiling with his arms out like he was about to embrace someone. I waited for him to come to me and then I realised he could not because he was chained to the floor."

She described his continued detention as "wrong" and "illegal", adding: "We want him released."

Slahi's brother said the family will not give up on securing his brother's release.

"We know he is innocent," he said.

President Barack Obama's attempts to close Guantanamo Bay have been blocked by Congress.

The most recent figures suggest 122 prisoners remain at the facility, including 54 who have been approved for transfer.