By Steve Swann
BBC home affairs correspondent
Ethiopian Binyam Mohamed is among those claiming damages
Up to 17 British intelligence officers allegedly colluded in the rendition and torture of seven former Guantanamo Bay detainees, the High Court has heard.
The allegations came during a claim for damages by some of the UK citizens and residents held at the facility in Cuba.
The security services' behaviour formed part of a wider pattern of misconduct, the counsel for the group said.
The government denied the claims and opposed an application to prevent the alleged destruction of vital documents.
The men are seeking a court order to appoint a supervisory solicitor to prevent papers which could back their damages claims from being destroyed.
A judgment on that is expected to be made on Thursday morning, but a date for the beginning of any civil action could be months, or even years, away.
Tim Otty, QC, for the former detainees, said they sought substantial damages from the government which had an obligation to establish a public inquiry into the issues.
He said: "The suffering experienced by these claimants has on any reckoning been intense".
Mr Otty told the court up to 17 intelligence officers were implicated in the mistreatment of the men.
He said they were involved in "aiding and abetting the extraordinary rendition and torture" of the men.
He added it formed part of a "much wider pattern of systemic misconduct and complicity".
It is not known for which agency the intelligence officers are employed or if there may be fewer officers using a number of different names.
Mr Otty warned the court that those "implicated in torture may not readily hand over evidence of their conduct" and said the protection of documents was the "central battleground" in the case.
Jonathan Crow, QC, representing the five government departments named in the action, said the government, as a litigant, could be trusted.
He denied the need for a supervisory solicitor overseeing documents because any rogue operators in the security services would "already have been able to cover their tracks".
He added it would be "against all our expectations" for there to be rogue operators.
The court heard MI5 had set up a Guantanamo review team, whose members are the only people authorised to have access to documents held in a secure storage area.
The Foreign Office alone was said to have identified "75 linear feet of documents".